A development apparatus for developing a latent electrostatic image formed on a latent electrostatic image bearing member to a visible image, having a development sleeve for transporting a developer to the latent electrostatic image for developing the same to a visible image, and a developer layer thickness regulating device for regulating the thickness of a developer layer on the development sleeve, in which development apparatus, the developer layer thickness regulation device comprises a pressure application member for applying pressure to the developer layer on the development sleeve by the magnetic force exerted on the pressure application member towards said developer transportation means, the pressure application member being supported so as to be movable in the direction substantially normal to the surface of the development sleeve.