Provided is an engine combustion chamber structure. Also provided is an inner wall structure for a through channel, through which exhaust gas or intake gas of the engine passes. An engine combustion engine structure is provided with a heat-insulating member on the inner wall of an engine constituent member which constitutes an engine combustion chamber, the heat-insulating member containing a heat-insulating porous layer formed from ceramics, and a surface dense layer formed on the surface of the heat-insulating porous layer and formed from ceramics. The surface dense layer of the heat-insulating member has an open porosity of 5% or less, and preferably the heat-insulating porous layer has a larger open porosity than the open porosity of the surface dense layer.