The object of the present invention is to provide a glow-plug engine capable of achieving suitable operation using a glow plug even for various kinds of fuel other than special alcohol based fuel. The end section of a glow plug protrudes inside a combustion chamber and is located in a specified area near the top surface 53a of piston when located at the top dead center. By doing so, it is possible to achieve suitable operation (combustion) using a glow plug even for various kinds of fuel other than special alcohol based fuels.