To provide a control valve for a liquid injection valve capable of quickly reducing pressure in a back pressure chamber and reducing ineffective injection time without enlarging an actuator in a liquid injection valve.

Since opening and closing of the control valve are done by pushing and pulling a cylindrical valve element 24 in and out an upper space 22f of a cylindrical seat body 22, pressure of high pressure fuel does not act in the drive direction of the cylindrical valve element 24. Consequently, the cylindrical valve element 24 can be driven by small drive force and the actuator is not enlarged. When the valve is opened, an opening is formed over a whole circumference of a tip of the cylindrical seat body 22, a discharge channel of large opening area is formed in a short time even with a little axial separation, and a great quantity of high pressure fuel can be discharged in a short period of time. A tip surface of a piston 24b separates from a bottom wall 22b and an orifice 22g opens, and assist force is generated on the piston 24b. Consequently, ineffectual injection time can be reduced without enlarging the actuator, and response of the fuel injection valve can be increased.