A motorcycle immobilizer amplifier mount structure that allows arrangement in the front portion of a motorcycle body to be simplified while reducing the size of an ignition switch, and prevents an immobilizer amplifier from being exposed to a high temperature of a combustion engine. In the immobilizer amplifier mount structure, immobilization signal output section is incorporated in an ignition switch unit, and the immobilizer amplifier amplifies an immobilization signal from the immobilization signal output section, and is mounted rearward of a cylinder head of the combustion engine on an inner surface of an intermediate portion, in a longitudinal direction, in a pair of left and right frame pieces forming a part of a motorcycle frame structure.