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, a resin bottle 8 is conveyed with a distance between the irradiating surface 12a and the resin bottle 8 being maintained constant. 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) for rotating the grippers 6 with respect to the rotary body 14 and forward/rearward moving means (18, 50) keeping constant a distance from the irradiating surface 12a of the electron beam irradiator are provided. In the electron beam irradiation region A, the gripper 6 is moved forward or rearward in a radial direction by the forward/rearward moving means in the electron beam irradiation region A to thereby maintain constant the distance between the resin bottle 8 and the electron beam irradiating surface 12a.
