To provide a pump device for lubricant which is downsized and reduced in cost due to a simplified decompression structure. A pump device S for lubricant comprising a pump main body 10 which is provided with a cylinder part 15 which suctions lubricant stored in a tank and discharges it from a discharge port 13 and a piston 30 and an actuator 40 which allows the piston 30 to move forward and backward, in which when lubricant is supplied to a lubrication pipeline W connected to the discharge port 13, the discharge port 13 is compressed, and when the supply of lubricant to the lubrication pipeline is stopped, the discharge port 13 is decompressed, wherein the piston 30 is allowed to move forward to the 1 st position P1 at which lubricant is discharged, move backward from the 1 st position to the 2 nd position P2 at which lubricant is suctioned and further move backward from the 2 nd position to the 3 rd position P3, and a decompression path 50 which is blocked when the piston is allowed to move between the 1 st position P1 and the 2 nd position P2, and is opened when the piston is moved backward to the 3 rd position is formed in the pump main body 10.