PURPOSE: To safely carry out the operation of cargo tilting, by enabling an elevating device for tilting a cargo box to be operated only when a pivoting section for tilting the cargo box in an optional direction is surely positioned in its locking condition.

CONSTITUTION: A solenoid SOL5 is energized by closing switches S1, S2 to change over a solenoid valve to a position where a pump is communicated with an operating cylinder in a cargo box pivoting section. One of switches S4 through S6 which corresponds to an optional tilting direction is closed to energize the corresponding solenoid valve SOL1 through SOL5 for changing over another selector valve so that the operating cylinder is communicated with and operated by the pump. When the selected pivoting section is completely locked, the corresponding limiting switch LS1 through LS4 is closed to energize a safety device A. Then the operating cylinder is locked by opening the above-mentioned closed switch S4 through S6. Further, when the selector valve is changed over by closing the switch S3 to energize a SOL6, a cargo box operating cylinder is communicated with and operated by the pump.