Radiation therapy apparatus and control method of radiation therapy apparatus

A radiation therapy apparatus that enhances the reliability and ease of use of a treatment is provided. A radiation therapy apparatus includes: a treatment bed moving a top plate with an object to be treated placed on the top plate to a predetermined treatment location; an imaging apparatus moving to the predetermined treatment location from a direction different from the direction of movement of the top plate and picking up an image of the object to be treated; and an irradiation apparatus provided between the treatment bed and the imaging apparatus, extensible, and applying a radioactive ray to the object to be treated. When the CT apparatus moves to the treatment location, the irradiation apparatus moves to a predetermined waiting position. When applying a radioactive ray to an object to be treated, the irradiation apparatus moves to a predetermined irradiation position.