An air-intake device having a noise reduction mechanism includes a surge tank connected to an intake manifold for introducing intake air into an internal combustion engine, an air duct connected to an upstream end of the surge tank and a resonator connected to the surge tank and the air duct. The resonator forms a resonator chamber connected to both the surge tank and the air duct. The surge tank is separated from the resonator chamber by a first vibrating member, and the air duct is separated from the resonator chamber by a second vibrating member. The noises in the surge tank are offset or reduced by resonating vibrations of the first vibrating member, and the noises in the air duct are offset or reduced by resonating vibrations of the second vibrating member. Thus, the intake air noises are effectively reduced by a simple combination of the resonator and the vibrating members.