To provide a fuel injector capable of freely adjusting timing for fuel injection without detaching a fuel injection pump.

The fuel injector comprises a pump housing 9 placed at a pump support 63 of an engine 51, a plunger 15, supported by the pump housing, for pressurizing the fuel and the fuel injection pump 1 connected to the plunger and including a tappet 31 facing a pump driving cam 67 of a camshaft 66. A roller 73 for transmitting motion of the pump driving cam to the tappet is disposed between the pump driving cam and the tappet. A timing adjusting mechanism 72 having bolts 93, 94 exposed outward is placed at the pump support. The timing adjusting mechanism varies timing for causing the pump driving cam to push up the tappet by moving the roller toward and away from a space between the pump driving cam and the tappet through operation of the bolts.