To provide a member for a microwave heating device using dielectric loss or magnetic loss.

In the present invention, a member for a microwave heating device, such as tableware, a cooker, a tray, and a wall material, to be used in the microwave heating device for heating by irradiation with a microwave, contains a dielectric or a magnetic substance of which permittivity or permeability becomes 0 or near 0 at a predetermined temperature (hereinafter referred to as a "heat-retaining temperature") or more in a temperature range to be heated by the microwave heating device. The heat-retaining temperature is determined at a temperature lower or higher than a desired temperature at the time of heating an object by using the microwave heating device. In addition, the member partially contains the dielectric or magnetic substance.