A silver halide photographic emulsion chemically sensitized by a sulfur compound of the formula: ##STR1## wherein R.sub.1 represents a 5-membered or 6-membered heterocyclic ring containing a nitrogen atom; R.sub.2 represents a hydrogen atom, a lower alkyl group, an allyl group, an aryl group, or an aralkyl group; and R.sub.3 has the same definition as R.sub.1 or R.sub.2 ; or R.sub.2 and R.sub.3 may join to form a heterocyclic ring; is disclosed.