PURPOSE: To obtain a new azo-based compound suitable as various photosensitive materials such as charge producing materials in electrophotographic photoreceptors, pigments, solar cells, etc., and a new diazonium salt as an intermediate suitable for its production.

CONSTITUTION: An azo-based compound expressed by formula I (A is coupler residue), e.g. a compound expressed by formula III and a diazonium salt expressed by formula II (X is anion) which is an intermediate for the compound. The compound expressed by formula I, e.g. a compound expressed by formula Ia is obtained by dropping sodium nitrite or nitrous acid into an acidic aqueous solution of an amine-based compound expressed by formula IV at a low temperature while stirring the acidic aqueous solution, then adding an acid to be an origin of the anion (X), providing a crystallized new tetrazonium salt expressed by formula IIa, subsequently adding a prescribed amount of a coupler expressed by the formula HA to the resultant tetrazonium salt and carrying out coupling reaction. Since the structure of m-terphenyl known as a quencher is introduced into the molecule of the compound expressed by formula I, its sensitivity is high and surface potential can be prevented from deteriorating by repeated use. Light stability is further excellent.