Manufacturing method of an oil-impregnated sintered bearing, comprising: forming a green compact from a raw powder with a forming mold; wherein the manufacturing method of an oil-impregnated sintered bearing further comprises: crushing vacancies opened on an outer peripheral surface of the green compact by pushing out the green compact from the forming mold, wherein the forming mold comprises a die, a core rod, a lower punch and an upper punch; - the core rod having a substantially circular cylindrical shape is placed coaxially in the die; - the lower punch is in a substantially circular cylindrical tubular shape and fits between the die and the core rod in such a way that the lower punch is able to move freely upwards and downwards; - the upper punch is in a substantially circular cylindrical tubular shape and fits between the die and the core rod in such a way that the upper punch is able to move freely upward and downward and to be detached from the die; a filling part is formed in the forming mold with the outer surface of the core rod, the inner peripheral surface of the die, the upper surface of the lower punch, and the lower surface of the upper punch; a rough part is formed on the inner peripheral surface of the die; a length of a region the rough part is formed in the longitudinal direction of the die substantially equals to the length of the green compact or is longer; an inner peripheral surface of the die between the rough part and a green compact exiting opening of the forming mold is mirror-like finished; and protrusions formed on the outer peripheral surface of the green compact body by the rough part are crushed by the rough part and by the mirror-like finished surface of the die during pushing out the green compact body through the green compact exiting opening of the forming mold. forming a green compact from a raw powder with a forming mold; wherein the manufacturing method of an oil-impregnated sintered bearing further comprises: crushing vacancies opened on an outer peripheral surface of the green compact by pushing out the green compact from the forming mold, wherein the forming mold comprises a die, a core rod, a lower punch and an upper punch; - the core rod having a substantially circular cylindrical shape is placed coaxially in the die; - the lower punch is in a substantially circular cylindrical tubular shape and fits between the die and the core rod in such a way that the lower punch is able to move freely upwards and downwards; - the upper punch is in a substantially circular cylindrical tubular shape and fits between the die and the core rod in such a way that the upper punch is able to move freely upward and downward and to be detached from the die; a filling part is formed in the forming mold with the outer surface of the core rod, the inner peripheral surface of the die, the upper surface of the lower punch, and the lower surface of the upper punch; a rough part is formed on the inner peripheral surface of the die; a length of a region the rough part is formed in the longitudinal direction of the die substantially equals to the length of the green compact or is longer; an inner peripheral surface of the die between the rough part and a green compact exiting opening of the forming mold is mirror-like finished; and protrusions formed on the outer peripheral surface of the green compact body by the rough part are crushed by the rough part and by the mirror-like finished surface of the die during pushing out the green compact body through the green compact exiting opening of the forming mold. crushing vacancies opened on an outer peripheral surface of the green compact by pushing out the green compact from the forming mold, wherein the forming mold comprises a die, a core rod, a lower punch and an upper punch; - the core rod having a substantially circular cylindrical shape is placed coaxially in the die; - the lower punch is in a substantially circular cylindrical tubular shape and fits between the die and the core rod in such a way that the lower punch is able to move freely upwards and downwards; - the upper punch is in a substantially circular cylindrical tubular shape and fits between the die and the core rod in such a way that the upper punch is able to move freely upward and downward and to be detached from the die; - the core rod having a substantially circular cylindrical shape is placed coaxially in the die; - the lower punch is in a substantially circular cylindrical tubular shape and fits between the die and the core rod in such a way that the lower punch is able to move freely upwards and downwards; - the upper punch is in a substantially circular cylindrical tubular shape and fits between the die and the core rod in such a way that the upper punch is able to move freely upward and downward and to be detached from the die; a filling part is formed in the forming mold with the outer surface of the core rod, the inner peripheral surface of the die, the upper surface of the lower punch, and the lower surface of the upper punch; a rough part is formed on the inner peripheral surface of the die; a length of a region the rough part is formed in the longitudinal direction of the die substantially equals to the length of the green compact or is longer; an inner peripheral surface of the die between the rough part and a green compact exiting opening of the forming mold is mirror-like finished; and protrusions formed on the outer peripheral surface of the green compact body by the rough part are crushed by the rough part and by the mirror-like finished surface of the die during pushing out the green compact body through the green compact exiting opening of the forming mold.