In a cooker according to the present disclosure, a convection heater for executing a convection mode and a circulation fan are disposed in a convection forming space that is in communication with a heating chamber, and a fan driver is disposed outside of the convection forming space. The cooker includes a leakage suppression mechanism for suppressing a microwave leak from the convection forming space. The leakage suppression mechanism is formed by a coaxial seal for setting a distance between opposing faces, i.e., between a circulation fan shaft passing through a first wall forming the convection forming space and the first wall to a predetermined distance or smaller. Therefore, a microwave leak from a mechanism for executing the convection mode is suppressed, and heat cooking with a microwave-heating mode can highly effectively be performed.