A negative pressure pump comprising: a housing that is formed in a shape of a tube having a bottom, and at which an opening portion is blocked by a cover body, and to whose interior lubricant is supplied, and in which a circular hole is formed at a position of a bottom portion, the position being eccentric from a housing center; a rotating shaft having a shaft portion that is fit-together with the circular hole, and having a supporting portion, whose diameter is larger than the shaft portion and that is disposed within the housing and whose outer peripheral surface contacts a portion of an inner wall surface of the housing, the rotating shaft rotating due to power being transmitted thereto from a power source; a vane that is disposed within the housing, and that is supported at the supporting portion of the rotating shaft so as to freely move reciprocally in a direction orthogonal to the rotating shaft, and that rotates integrally with the rotating shaft, and whose end portions slide on the inner wall surface, and that sections an interior of the housing into a plurality of spaces; an intake portion that is formed in the housing and takes a gas into the housing; and a discharging portion that is formed further toward a rotating direction downstream side of the vane than the intake portion of the housing, and that discharges gas, that has been sucked-in from the intake portion, and the lubricant to an exterior of the housing; characterized by a concave portion that is formed in a bottom surface of the housing and, in a rotating direction of the vane, between the discharging portion and a portion of the inner wall surface that the supporting portion contacts, and that communicates with the circular hole, and guides the lubricant, that is moved by the vane, to the circular hole. a housing that is formed in a shape of a tube having a bottom, and at which an opening portion is blocked by a cover body, and to whose interior lubricant is supplied, and in which a circular hole is formed at a position of a bottom portion, the position being eccentric from a housing center; a rotating shaft having a shaft portion that is fit-together with the circular hole, and having a supporting portion, whose diameter is larger than the shaft portion and that is disposed within the housing and whose outer peripheral surface contacts a portion of an inner wall surface of the housing, the rotating shaft rotating due to power being transmitted thereto from a power source; a vane that is disposed within the housing, and that is supported at the supporting portion of the rotating shaft so as to freely move reciprocally in a direction orthogonal to the rotating shaft, and that rotates integrally with the rotating shaft, and whose end portions slide on the inner wall surface, and that sections an interior of the housing into a plurality of spaces; an intake portion that is formed in the housing and takes a gas into the housing; and a discharging portion that is formed further toward a rotating direction downstream side of the vane than the intake portion of the housing, and that discharges gas, that has been sucked-in from the intake portion, and the lubricant to an exterior of the housing; characterized by a concave portion that is formed in a bottom surface of the housing and, in a rotating direction of the vane, between the discharging portion and a portion of the inner wall surface that the supporting portion contacts, and that communicates with the circular hole, and guides the lubricant, that is moved by the vane, to the circular hole.