To reduce contamination in the washing tank of an automatic processing machine and to prevent the color stain of a silver halide photographic sensitive material after processing by supplying an oxidizing agent-contg. thick soln. or solid agent while mixing with water in the washing tank after a fixing step when the sensitive material contg. a specified compd. is washed after it is imagewise exposed, developed and fixed.

When a silver halide photographic sensitive material contg. a compd. represented by the formula or the like is washed 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 Z1 and Z2 is a group of nonmetallic atoms required to form an optionally substd. benzo or naphtho condensed ring, each of R1-R6 is alkyl, each of R1-R6, Z1 and Z2 is a group which makes it possible for each dye molecule to have a substituent having two acid substituents or one -CH2CH2 OR group, L is methine, X is an anion, (m) is 4 or 5 and (n) is 1 or 2.