PURPOSE: To increase color density in a short processing time by forming a magenta coupler-contg. layer by casting a soln. contg. a specified 4-equiv. magenta coupler and a thiosulfonic ester compd.

CONSTITUTION: A magenta coupler-contg. layer is formed by casting a casting soln. contg. a 4-equiv. magenta coupler represented by formula I and a thiosulfonic ester compd. In the formula I, (n) is 1-5, (m) is 1-3, R1 is halogen, alkoxy, alkylthio, acylamino, carbamoyl, sulfonamido, sulfamoyl or alkoxycarbonyl and R2 is halogen, cyano, thiocyanate, alkoxy, alkyl, acylamino, carbamoyl, sulfonylamido, sulfamoyl or alkoxycarbonyl. A color image having high color density immediately after processing can be formed even in the case of a shortened processing time.