An electrically operated valve comprising: a valve main body having a valve seat; a motor including: a stator fixed to the valve main body, and a rotor driven to rotate with respect to the stator, a planetary gear type deceleration mechanism configured to decelerate rotation of the rotor to transmit to an output gear; a valve member configured to be movable toward and away from the valve seat in an axial direction; and a feed screw mechanism configured to convert rotational movement of the output gear into movement of the valve member in the axial direction; wherein: the planetary gear type deceleration mechanism includes: a sun gear coupled to the rotor, wherein a shaft passes through the sun gear in the axial direction, a planetary gear engaged with the sun gear, a carrier for rotatably supporting the planetary gear, comprising a lower disk having a circular opening at the center thereof through which the shaft passes through, an annular ring gear engaged with the planetary gear, wherein the output gear is formed in a cylindrical shape with a bottom that has a number of inner teeth that differs from the number of teeth of the ring gear, and engages with the planetary gear, characterized in that the sun gear comprises an annular boss at its axial end, and in that the planetary gear type deceleration mechanism further includes a sliding member abutting against the annular boss of the sun gear, wherein the sliding member is made of a different material from the material of the sun gear. a valve main body having a valve seat; a motor including: a stator fixed to the valve main body, and a rotor driven to rotate with respect to the stator, a planetary gear type deceleration mechanism configured to decelerate rotation of the rotor to transmit to an output gear; a valve member configured to be movable toward and away from the valve seat in an axial direction; and a feed screw mechanism configured to convert rotational movement of the output gear into movement of the valve member in the axial direction; wherein: the planetary gear type deceleration mechanism includes: a sun gear coupled to the rotor, wherein a shaft passes through the sun gear in the axial direction, a planetary gear engaged with the sun gear, a carrier for rotatably supporting the planetary gear, comprising a lower disk having a circular opening at the center thereof through which the shaft passes through, an annular ring gear engaged with the planetary gear, wherein the output gear is formed in a cylindrical shape with a bottom that has a number of inner teeth that differs from the number of teeth of the ring gear, and engages with the planetary gear, characterized in that the sun gear comprises an annular boss at its axial end, and in that the planetary gear type deceleration mechanism further includes a sliding member abutting against the annular boss of the sun gear, wherein the sliding member is made of a different material from the material of the sun gear. a stator fixed to the valve main body, and a rotor driven to rotate with respect to the stator, a planetary gear type deceleration mechanism configured to decelerate rotation of the rotor to transmit to an output gear; a valve member configured to be movable toward and away from the valve seat in an axial direction; and a feed screw mechanism configured to convert rotational movement of the output gear into movement of the valve member in the axial direction; wherein: the planetary gear type deceleration mechanism includes: a sun gear coupled to the rotor, wherein a shaft passes through the sun gear in the axial direction, a planetary gear engaged with the sun gear, a carrier for rotatably supporting the planetary gear, comprising a lower disk having a circular opening at the center thereof through which the shaft passes through, an annular ring gear engaged with the planetary gear, a sun gear coupled to the rotor, wherein a shaft passes through the sun gear in the axial direction, a planetary gear engaged with the sun gear, a carrier for rotatably supporting the planetary gear, comprising a lower disk having a circular opening at the center thereof through which the shaft passes through, an annular ring gear engaged with the planetary gear, wherein the output gear is formed in a cylindrical shape with a bottom that has a number of inner teeth that differs from the number of teeth of the ring gear, and engages with the planetary gear, characterized in that the sun gear comprises an annular boss at its axial end, and in that the planetary gear type deceleration mechanism further includes a sliding member abutting against the annular boss of the sun gear, wherein the sliding member is made of a different material from the material of the sun gear.