To obtain a new monoazo compound excellent in tone, capable of providing a vivid image having magenta color and high color concentration, excellent in weatherability, heat resistance and heat-resistant transfer property and useful for heat-sensitive transfer sheets.

This compound is represented by the formula [X1 and X2 are each H, a halogen or CN, especially a halogen such as Cl; Y1 and Y2 are each a halogen such as Cl, H, a (substituted)alkyl, a (substituted)amino or a (substituted)OH; Z is a coupling group capable of forming a ring such as 5-membered ring or 6-membered ring], e.g. 1-[(6,7-dichlorobenzotiazol-2-yl)azo]-2- methyl-4-morpholinobenzene. The compound of the formula is obtained by diazotizing the corresponding 2-aminobenzothiazole derivative with nitrosylsulfuric acid in a mineral acid at -5 to 10°C and subjecting the resultant diazo solution to coupling with the corresponding aniline derivative in an acid medium at -5 to 20°C.