To obtain the subject composition equipped with a low temperature- curing property and preservation stability simultaneously and capable of forming a membrane excellent in waterproof property, soil resistance, etc. by containing a specific polyhydrazine compound with a specific photostabilizer and/or an ultraviolet absorbing agent.

This hydrazine derivative composition contains (A) a polyhydrazine compound having ≥2 hydrazine residues in one molecule, (B) a photostabilizer containing carbonyl group (preferably a hindered amine derivative) and/or an ultraviolet absorbing agent. The component A is preferably a semicarbazide derivative composition of the formula [R1 is a 2-20C alkylenediisocyanate, a 5-25C cycloalkylenediisocyanate or the like; R2 is H or a 1-20C alkyl; R3 is a 1-20C alkylene, a 5-20C cycloalkylene or the like; (n) is 0, 1; and (l), (m) are each 0 or a positive integer, provided that 20≥(l+m)≥3]. The composition is useful as a curing agent for a polycarbonyl compound, etc.