Abstract: To provide an engine capable of more quickly decreasing an auxiliary chamber gas pressure and ensuring a favorable load responsiveness. A gas engine is an engine including, as combustion chambers of each cylinder, an auxiliary chamber that ignites fuel gas to generate flame and a main chamber that combusts the mixture of fuel gas and air using the flame generated in the auxiliary chamber, and includes an auxiliary chamber main pipe that supplies the fuel gas to the auxiliary chamber, an air supply passage in which the air to be supplied to the main chamber flows, and a connection pipe communicating from the auxiliary chamber main pipe to the air supply passage.