To obtain a heat sensitive adhesive having sufficient adhesion, good in blocking resistance, having no dusting and excellent in printing properties, and further to obtain a heat sensitive adhesive sheet.

This heat sensitive adhesive consisting essentially of a thermoplastic resin and a solid plasticizer includes the thermoplastic resin containing a thermoplastic resin M having 60-150°C glass transition temperature and a thermoplastic resin N having (-30) to 30°C glass transition temperature regulated so that the solid weight ratio of the thermoplastic resins M/N may be (55/45) to (98/2).