To provide a pump for a braking system increasing sealing performance between a piston and bore and motion performance and durability of the piston and facilitating assembling property.

On the pump for the braking system, the bore 210 formed on a modulator block 200 and connected to a suction port 211 and a delivery port 212; the piston 300 formed with an oil flow passage 310 installed on the bore 210 and transferring the oil from the suction port 211 to the delivery port 212; an inlet valve 500 for opening/closing the oil flow passage 310 and an outlet valve 700 for opening/closing delivery of the compressed oil; a guide member 401 fixed to the bore 210, provided on an outer side of the piston 300 and guiding motion of the piston 300; and a fixing unit 400 including a sealing member 402 fixed to the bore 210, provided on the outer side of the piston 300 and maintaining airtight property between the bore 210 and the piston 300 are provided.