An antitheft device enables a vehicle to continue its operation without reexecuting information transmissions by referring to stored reception information when a power supply is instantaneously interrupted and recovered. The antitheft device includes an operation-equipment limiting part, a switch for sending a first ID code, an operation-equipment operation determining part that receives the first ID code and generates permission information for releasing a limited state of an operation equipment, a nonvolatile memory for storing the permission information, and an engine operation limiting part that permits the operation of the engine in response to the permission information, and limits the operation of the engine based on an operating condition of the engine. When the result of collation of the first ID code with a second ID code indicates coincidence, the operation-equipment operation determining part generates permission information to enable the operation equipment to operate, and makes the permission information stored in the nonvolatile memory.