To provide a mattress for an operating table capable of preventing a bedsore generated during an operation and keeping a body temperature.

This mattress 10 mounted on the operating table for reducing a body pressure applied to a person to be operated and preventing body temperature decline during the operation is constituted of first foam 14 which is the sheet of a low restitution coefficient for mounting the person to be operated capable of securing a large body contact area to the person to be operated, second foam 16 which is the sheet of a high restitution coefficient mounted on the operating table for stably holding the person to be operated on the operating table by being positioned on the back side of the first foam, an electric heater 18 disposed between the first and second foam for heating the person to be operated through the first foam, first temperature sensors 22 disposed on the surface side of the first foam for detecting the body temperature of the person to be operated at plural parts and a controller 26 for comparing temperature information from the plural first temperature sensors with a target body temperature set for the person to be operated and controlling the energizing state of the electric heater.