A control system of an industrial truck includes a first switch, a second switch and a hydraulic circuit. The first switch detects whether an operator sits on a seat, and carries out a first operation based on the result. The second switch detects whether a device for operating an actuator is operated, and carries out a second operation based on the result. The hydraulic circuit is used for operating the actuator. It a control valve, a first circulating line, a hydraulic line and a drive lock valve. The control valve includes a spool whose position is changed by the device. The first circulating line includes the control valve, through which the hydraulic fluid circulates. The hydraulic line connects the spool with the actuator. The drive lock valve is provided for the hydraulic line and blocks the hydraulic line, based on the first operation and/or the second operation.