To provide a heat generating evaporation tray which eliminates the possibility of breakage by cooking using heat in a microwave oven and a heating medium material of the heat generating tray for the microwave oven optimum for manufacture of this heat generating tray.

A thin film of ferrite is attached and fixed integrally via a glassy material integrated with glaze to the bottom of a tray body which is made of low- expansion pottery having excellent heat resistance and thermal impact resistance and is subjected to the application of the glaze on its surface. The thin film of the ferrite substantially comprises the heating medium material composed to a transfer paper structure by successively laminating a flux layer, a ferrite layer and a flux layer on a mount, printing these layers, holding the ferrite layer to a sandwich structure with the flux layers and covering the surfaces with cover coating layers. This heating medium material is transferred to the bottom of a tray body by stripping the mount and is fired, by which the glaze of the tray body and flux of the heating medium material are melted and integrated and the heating medium material is installed and fixed to the bottom of the tray body.