In an irradiation region A in which an electron beam irradiator emits an electron beam through an irradiating surface 12a of the electron beam irradiator, areas B and D are formed in which one surface of a rectangular resin bottle 8 is in parallel with the irradiating surface 12a. Grippers 6 are arranged to an outer peripheral portion of a rotary body 14 in a circumferential direction thereof at an equal interval, and the resin bottles 8 are conveyed with neck portions 8a thereof being held. Rotating means (52, 58, 62) that rotate the grippers 6 with respect to the rotary body 14 and forward/rearward moving means (18, 50) that keeps constant a distance from the irradiating surface 12a of the electron beam irradiator are provided. In the electron beam irradiation region A, by rotating the gripper 6 by the rotating means, the resin bottle 8 is moved while maintaining one surface of the rectangular resin bottle 8 to be in parallel with the flat irradiating surface 12a.
