An image forming apparatus includes a cartridge unit and a cartridge support member. The cartridge unit includes a photosensitive drum on a surface of which an electrostatic latent image is to be formed. The cartridge support member supports the cartridge unit inside an apparatus main body. The cartridge unit is detachable from the apparatus main body. In a case where the cartridge unit is attached to the apparatus main body, a Helmholtz resonator including a communication portion and including a cavity portion is constituted of the cartridge unit and the cartridge support member. The cartridge unit includes at least a part of the communication portion of the Helmholtz resonator.