To ensure high max. density and low fog contrasty good image quality and to improve the stain of a silver halide photographic sensitive material and contamination with fur, algae, a dye, etc., by supplying an oxidizing agent- contg. thick soln. or solid agent while mixing with water in a washing tank after a fixing step when the sensitive material contg. a specified spectral sensitizing dye is washed after it is imagewise exposed, developed and fixed.

When a silver halide photographic sensitive material contg. a spectral sensitizing dye represented by the formula is washed with oxidizing agent-contg. washing water after it is imagewise exposed, developed and fixed, an oxidizing agent-contg. thick soln. or solid agent is supplied while mixing with water in a washing tank after the fixing step. In the formula, each of R11 and R12 is alkyl, R13 is H, alkyl or alkoxy, D11 is a group of nonmetallic atoms required to complete a divalent ethylene bond, each of Z11 and Z12 is a group of nonmetallic atoms required to complete a 5- or 6-membered nitrogen- contg. heterocycle, X1 is an acid anion and (n) is 1 or 2.