There is provided a radiation-irradiation device of which a direction can be easily changed obliquely with a simple structure. A rear wheel unit (12R) of a radiation-irradiation device includes first locking means that includes a front operating portion (109F) of a brake pedal (109), a shaft (108), a gear (107), a cam (106), a rod (104), a lever (105), and a disc (103) and restrains the traveling rotation of a wheel (102). Further, the rear wheel unit (12R) includes second locking means that includes a rear operating portion (109R) of the brake pedal (109), the shaft (108), the gear (107), and the cam (106) and restrains the revolution of a casing (101).