diameter of spool 26 d 2 is a diameter of piston hole 30 and d 3 is a diameter of second piston 34 now spool 26 moving from first position a to neutral position n will be described by switching operation valve 2 from first position 1 to neutral position n spool 26 is moved toward the neutral position by the return pressure oil of oil hydraulic motor 5 and spring 27 the pressure oil of left pressure reception chamber 28 and the pressure oil of pressure reception chamber 32 are discharged into first pump port 22 when spool 26 is moved from first position a to stroke l 2 namely the start of the stroke the communication area of first pump port 22 with left pressure reception chamber 28 and with pressure reception chamber 32 is large to a 2 a 3 a 4 and spool 26 is moved quickly when spool 26 is moved from stroke l 2 to stroke l 1 namely middle stroke the communication area of first pump port 22 with left pressure reception chamber 28 and with pressure reception chamber 32 is small to a 3 a 4 and spool 26 is moved slowly when spool 26 is moved from stroke l 1 to neutral position n namely the end of the stroke the communication area of first pump port 22 with left pressure reception chamber 28 and with pressure reception chamber 32 is intermediate to a 1 a 3 a 4 so that spool 26 is moved at an intermediate speed and when spool 26 is moved from first position a to neutral position n the communication area of right pressure reception chamber 29 with second motor port 25 is a 1 a 3 which is an intermediate value between.