Common-rail injector

A common rail injector (1) for injecting fuel through a high-pressure channel (12) includes a control chamber (4), a control valve (102), and a drive unit (101). The control chamber (4) applies pressure to a nozzle needle (5). The control valve (102) switches communication of the control chamber (4) between the high-pressure channel (12) and a low-pressure channel (13). The drive unit (101) selectively sets a valve element (2) of the control valve (102) on a low-pressure side seat (22) or a high-pressure side seat (23). The drive unit (101) has an actuator (6) and a slide pin member (3). The slide pin member (3) slides inside a slide hole (31) to transmit a force to the valve element (2). A diameter of the low-pressure side seat (22) is less than or equal to a diameter of the high-pressure side seat (23). The pressure in the control chamber (4) is exerted as an assistance force, so that a high-pressure side seat closing load becomes less than or equal to a low-pressure side seat opening load.