PURPOSE: To provide a control mechanism capable of creating hydraulic control state suitable for operation conditions and simultaneously free from causing worsening of working environment by hydraulic noise.

CONSTITUTION: In a control mechanism of a working vehicle provided with a controller 10 for carrying out change over control of a hydraulic control valve V to a hydraulic cylinder CY for subjecting relative posture of the working apparatus to changing operation, the hydraulic control valve V is constituted of an electromagnetic proportional flow rate control valve capable of changing and controlling a hydraulic opening based on feed electric current and the controller 10 is provided with an on-off control mode for carrying out changeover control of a hydraulic control valve V so as to alternately provide wholly opening position and wholly closing position and a proportional control mode for successively changing the opening while properly changing it and when it is detected by a sensor 14 for detecting number of revolutions that number of revolutions is setting value or above it is detected by a speed change position detecting sensor 15 that variable speed gear for travelling is positioned at high speed, this control mechanism is constituted so as to carry out control by on-off control mode.