A gas engine regulator includes a decompression chamber defined internally of the regulator and having a gas inlet through which liquefied gas fuel enters and a gas outlet through which the gas fuel exits. The gas inlet is provided at one end side of the decompression chamber while the gas outlet is provided at an opposite end side laterally spaced via a space from the one end side. The regulator also includes a partitioning wall disposed to surround the gas outlet and having a gas passage communicating with the gas outlet, the gas passage having a passage inlet disposed upwardly of the gas inlet.