Disclosed herein is a gear actuator for a double clutch transmission, which includes a power module (100), including odd and even-numbered stage select solenoids and shift motors, a controller directly connected to them, and select levers connected to select rods of the select solenoids, shift modules (200) for transmitting the rotational forces of the shift motors to a control shaft assembly (300), the control shaft assembly (300) for transmitting the operating force of the power module (100) to a shift lug, and a body housing (400) having the power module (100), the shift modules (200), and the control shaft assembly (300) installed therein. Accordingly, the gear actuator can have a more compact structure and be easily assembled by modularization.