A boom control valve and a pulsation absorption control valve are provided in the halfway point of a center bypass line. The pulsation absorption control valve is arranged in a position downstream of the boom control valve. The pulsation absorption control valve is switched to a blockade position and a communication position by a pilot pressure from a remote control valve. The pulsation absorption control valve is constituted such that one main line out of a pair of main lines is communicated with or blocked off from an accumulator via one communication line and the other main line is communicated with or blocked off from the side of a tank via the other communication line. The accumulator is operated as a dynamic damper at the traveling of a vehicle. This arrangement enables the construction of the communication line to be simplified, thus improving operability at assembling.