An industrial vehicle comprising: an engine; a hydraulic pump driven by the engine; a hydraulic actuating device (15,16) actuated by hydraulic oil; a connection oil passage (23,38,40) connecting the hydraulic pump and the hydraulic actuating device (15,16); a supply oil passage (45,46) through which hydraulic oil to be supplied to the hydraulic actuating device (15,16) passes; a discharge oil passage through which hydraulic oil to be discharged to an oil tank passes; an unloading valve connecting the supply oil passage (45,46) and the discharge oil passage; a relief pressure valve connected to the supply oil passage (45,46) and actuated by pressure of the hydraulic oil passing through the supply oil passage (45,46); a timer circuit unit (52,54,56) connected to the supply oil passage (45,46) and opening the supply oil passage (45,46) when a certain time period has elapsed; characterized by the supply oil passage (45,46) comprising a first supply oil passage connected to the hydraulic actuating device (15,16) and a second supply oil passage diverging from the connection oil passage (23,38,40); the relief pressure valve being connected to the first supply oil passage; the timer circuit unit (52,54,56) comprising: an on-off valve connected to a diverging oil passage and opening or closing the diverging oil passage, the diverging oil passage diverging from the first supply oil passage; a check valve connected to the second supply oil passage and applying pressure of the second supply oil passage to the on-off valve when the unloading valve is put into a closed state; and an orifice connected to the second supply oil passage and releasing pressure applied to the on-off valve to the first supply oil passage through the second supply oil passage when the unloading valve is put into an open state; and a control unit controlling a state of the unloading valve between an open state and a closed state, wherein the control unit switches the state of the unloading valve to an open state when a load is applied to the engine in a state where operation of the hydraulic actuating device (15,16) is allowed and switches the state of the unloading valve to an open state while operation of the hydraulic actuating device (15,16) is restricted. an engine; a hydraulic pump driven by the engine; a hydraulic actuating device (15,16) actuated by hydraulic oil; a connection oil passage (23,38,40) connecting the hydraulic pump and the hydraulic actuating device (15,16); a supply oil passage (45,46) through which hydraulic oil to be supplied to the hydraulic actuating device (15,16) passes; a discharge oil passage through which hydraulic oil to be discharged to an oil tank passes; an unloading valve connecting the supply oil passage (45,46) and the discharge oil passage; a relief pressure valve connected to the supply oil passage (45,46) and actuated by pressure of the hydraulic oil passing through the supply oil passage (45,46); a timer circuit unit (52,54,56) connected to the supply oil passage (45,46) and opening the supply oil passage (45,46) when a certain time period has elapsed; characterized by the supply oil passage (45,46) comprising a first supply oil passage connected to the hydraulic actuating device (15,16) and a second supply oil passage diverging from the connection oil passage (23,38,40); the relief pressure valve being connected to the first supply oil passage; the timer circuit unit (52,54,56) comprising: an on-off valve connected to a diverging oil passage and opening or closing the diverging oil passage, the diverging oil passage diverging from the first supply oil passage; a check valve connected to the second supply oil passage and applying pressure of the second supply oil passage to the on-off valve when the unloading valve is put into a closed state; and an orifice connected to the second supply oil passage and releasing pressure applied to the on-off valve to the first supply oil passage through the second supply oil passage when the unloading valve is put into an open state; and a control unit controlling a state of the unloading valve between an open state and a closed state, wherein the control unit switches the state of the unloading valve to an open state when a load is applied to the engine in a state where operation of the hydraulic actuating device (15,16) is allowed and switches the state of the unloading valve to an open state while operation of the hydraulic actuating device (15,16) is restricted. an on-off valve connected to a diverging oil passage and opening or closing the diverging oil passage, the diverging oil passage diverging from the first supply oil passage; a check valve connected to the second supply oil passage and applying pressure of the second supply oil passage to the on-off valve when the unloading valve is put into a closed state; and an orifice connected to the second supply oil passage and releasing pressure applied to the on-off valve to the first supply oil passage through the second supply oil passage when the unloading valve is put into an open state; and a control unit controlling a state of the unloading valve between an open state and a closed state, wherein the control unit switches the state of the unloading valve to an open state when a load is applied to the engine in a state where operation of the hydraulic actuating device (15,16) is allowed and switches the state of the unloading valve to an open state while operation of the hydraulic actuating device (15,16) is restricted.