PURPOSE: To make the temps. of the stages in a container uniform by generating glow discharge in the vicinity of inner wall bodies, through independently variable resistors, electrically insulated to each other and set round a plurality of products to be treated.

CONSTITUTION: Vacuum container 1 is evacuated to about 10-3 Torr, and use gas such as N2-H2 mixed gas is introduced into container 1 up to a treatment press., e.g. 0.1W20 Torr. A discharge voltage is then applied to products 6a, 6b, 6c to be treated and holding stands 5a, 5b, 5c from ion treatment DC power source 8 through gap plates 11a, 11b, 11c and inner wall bodies 7a, 7b, 7c, whereby each of the products and each of the stands generate glow discharge in the space between them and each of the bodies. At this time, by adjusting the electrode gaps of plates 11a, 11b, 11c with handles 13a, 13b, 13c and changing water resistance in water tank 12 the power supplied to the products and the stands is regulated so that the temps. of the product stages are made uniform.