A hydraulic pump with an unloading function which comprises a pump body, a spring chamber formed in the pump body and communicating with a fluid reservoir, a pump chamber formed in the pump body and communicating with the spring chamber and an accumulator through a suction valve and a delivery valve, respectively. An operation chamber is also formed in the pump body and accommodates a drive member such as a pump drive shaft. A plunger slidably extending through a first partition between the spring chamber and the pump chamber, and a tappet having a smaller diameter than that of the plunger and slidably extends through a second partition between the pump chamber and the operation chamber to abut against the plunger. A spring is accommodated in the spring chamber and is adapted to apply a predetermined resilient force to the plunger to bias it toward the tappet.