PURPOSE: To facilitate uniform treatment of wafers by a method wherein protruding guides are formed on the inner surfaces of the side walls of a wafer holder along the direction of inserting wafers and the guides are not formed on insertion stoppers which are formed as continuous surfaces which touch the circumference surfaces only.

CONSTITUTION: A wafer holding space 8 is composed of a part defined by the side walls 3 and 3, the side plates 4 and 4 and the bottom plates 6 and 6 of a wafer holder 1 and a plurality of protruding guides 7 and 7 are formed on the side walls 3 and 3 from the top ends of their width direction toward the bottom plates 6 and 6. The guides 7 and 7 have functions such that they guide insertion of wafers 2 into the holding space 8 and support the respective held wafers 2 in parallel with predetermined intervals in the holding space 8. The protruding guides 7 and 7 are formed on the inner surface of the side walls 3 and 3 only and are not formed on the inner sides of the bottom plates 6 and 6, which are receptacles for the wafers and are formed as continuous flat or bent surfaces. With this constitution, contact areas between the wafer surfaces and the guides can be reduced and uniform treatment over the wide areas can be realized when the wafers are treated with chemicals or cleaning agents.