Grille shutter device at a front portion of a vehicle

A grille shutter device includes a shutter mechanism (11) provided within a grille opening portion formed at a front portion of a vehicle body and configured to control a flow rate of air into the vehicle body, a drive device (12) driven by a motor (18) to open and close the shutter mechanism, and a control device (20) supplying a driving power to the motor. The control device includes a drive circuit (22) provided at a portion of a power supply passage (Lp) between an in-vehicle power source (21) and the motor (18), a control circuit (23) controlling a duty ratio of the drive circuit (22), and a power supply voltage detection portion (27, 23) detecting a power supply voltage (Vb) of the in-vehicle power source. The control circuit includes a correction portion (23) correcting the duty ratio based on the power supply voltage (Vb) to restrain a change of a speed of the motor (18) caused by a fluctuation of the power supply voltage (Vb).