A hydraulic motor comprising: a rotation shaft; a housing comprising a plurality of cylinder parts each of which extends along a radial direction relative to the rotation shaft; a plurality of pistons which are arranged in the plurality of the cylinder parts, respectively, and which form a plurality of working chambers with the plurality of the cylinder parts, respectively; a converting mechanism for performing conversion between rotational motion of the rotation shaft and reciprocating motion of the plurality of the pistons; a plurality of high pressure valves for controlling supply of working fluid to the plurality of the working chambers, respectively; a plurality of low pressure valves for controlling discharge of working fluid from the plurality of the working chambers, respectively; at least one auxiliary valve for controlling, independently of the plurality of the high pressure valves, supply of the working fluid to at least one of the plurality of the working chambers; and a plurality of valve blocks which are fixed to the housing and to which the plurality of high pressure valves and the plurality of low pressure valves are attached, respectively, the hydraulic motor being characterized in that the at least one auxiliary valve has a cross-sectional passage area smaller than respective ones of the plurality of the high pressure valves, the at least one auxiliary valve is attached to at least one of the plurality of valve blocks, the valve block comprises a valve-block high-pressure passage inside the valve block to supply the working fluid to the working chamber, and the valve-block high-pressure passage comprises: a main flow part where the high pressure valve is arranged; and a bypass part which is provided in parallel to the main flow part to bypass the high pressure valve and where the auxiliary valve is arranged. a rotation shaft; a housing comprising a plurality of cylinder parts each of which extends along a radial direction relative to the rotation shaft; a plurality of pistons which are arranged in the plurality of the cylinder parts, respectively, and which form a plurality of working chambers with the plurality of the cylinder parts, respectively; a converting mechanism for performing conversion between rotational motion of the rotation shaft and reciprocating motion of the plurality of the pistons; a plurality of high pressure valves for controlling supply of working fluid to the plurality of the working chambers, respectively; a plurality of low pressure valves for controlling discharge of working fluid from the plurality of the working chambers, respectively; at least one auxiliary valve for controlling, independently of the plurality of the high pressure valves, supply of the working fluid to at least one of the plurality of the working chambers; and a plurality of valve blocks which are fixed to the housing and to which the plurality of high pressure valves and the plurality of low pressure valves are attached, respectively, the hydraulic motor being characterized in that the at least one auxiliary valve has a cross-sectional passage area smaller than respective ones of the plurality of the high pressure valves, the at least one auxiliary valve is attached to at least one of the plurality of valve blocks, the valve block comprises a valve-block high-pressure passage inside the valve block to supply the working fluid to the working chamber, and the valve-block high-pressure passage comprises: a main flow part where the high pressure valve is arranged; and a bypass part which is provided in parallel to the main flow part to bypass the high pressure valve and where the auxiliary valve is arranged. a main flow part where the high pressure valve is arranged; and a bypass part which is provided in parallel to the main flow part to bypass the high pressure valve and where the auxiliary valve is arranged.