In a gas-engine-mounted working machine, a gas engine is mounted on a machine body and supplied with fuel gas from a cassette gas canister. The cassette gas canister is detachably attached to a gas canister retainer assembly. Handle column extends rearwardly and upwardly from the machine body and having left and right handle posts fixed to the machine body for supporting an operating handle of the machine. The cassette gas canister is mounted, via the gas canister retainer assembly, between the left and right handle posts.
