PURPOSE: To make it possible to easily trap gas particles onto cryopanels and to make gas particles difficult to fly away outward, thereby it is possible to aim at enhancing the characteristic of gas discharge, by providing looper type buffles whose directions of inclination are reversed with the boundary at the center between adjacent cryopanels.

CONSTITUTION: A cryopump 13 is composed of a plurality of cryopanels 8, radiation shield plates 10 surrounding the cryopanels 8, a front surface shield plate 10, and a plurality of looper type buffles 14, 15 positioned on the front surface of the cryopump 13. The directions of inclination of looper buffles 14, 15 are reversed with the boundary at the center between adjacent cryopanels 8. With this arrangement gas particles 6 flow into the cryopump 13 through a front opening 16, and then impinges and reflects upon the radiation shield plate 10. Then a sustantial part of gas particles impinges upon the cryopanel 8 and is therefore trapped thereon. Gas particles which have returned to the front surface side, impinge upon the looper type buffles 14, 15 and therefore become difficult to fly away outward.