A developer for a silver halide photographic photosensitive material containing at least one of monocyclic dimercaptotriazine compounds, bis-type dimercaptotriazine compounds, mercapto-1,2,4-triazine compounds and dimercaptopyrimidine compounds, and a process for developing a silver halide photographic photosensitive material using the developer. The compounds of the present invention provides excellent effect in preventing silver stains without affecting the photographic properties of the photographic material.