Describes herein are a microscope optical module, a microscope, a control device for the microscope optical module, and multiphoton excitation microscope, which can switch the observation field of view at high speed and observe a large field of view. The microscope optical module includes an optical-axis-shifting optical system having an optical element, an optical-axis-shifting optical system support for positioning the optical-axis-shifting optical system with respect to the objective light flux of the microscope, and a rotator arranged on the optical-axis-shifting optical system support, the rotator rotatably supporting the optical-axis-shifting optical system with respect to the optical axis of the objective light flux, wherein the microscope optical module is added to an objective light flux side of a microscope.