An electric lawn mower comprising: a mower body including an electric motor, a cutting blade rotatably driven by the electric motor for mowing a lawn, a battery, and a battery mount device configured to be able to hold the battery, the electric motor being driven with a supply of an electric power from the battery; and an unauthorized use preventing device (30, 31) configured to prevent an unauthorized use of the electric lawn mower, wherein: the unauthorized use preventing device (30, 31) includes a key and a key receiver, and the key receiver is disposed on the mower body at a position proximal to the battery mount device, wherein: the unauthorized use preventing device comprises a lock mechanism including the key and the key receiver configured as a key insertion portion for locking and unlocking the electric motor; when the key is inserted into the key insertion portion, the electric motor is unlocked and can be started; the key insertion portion is disposed proximal to the battery mount device; the battery mount device includes a battery mount base and a battery cover; the battery mount base is disposed on the mower body and configured to be able to hold the battery; the battery cover is configured to be able to cover the battery mount base and can be opened and closed; characterised in that the key insertion portion is positioned so as to be covered by the battery cover when the battery cover is closed. a mower body including an electric motor, a cutting blade rotatably driven by the electric motor for mowing a lawn, a battery, and a battery mount device configured to be able to hold the battery, the electric motor being driven with a supply of an electric power from the battery; and an unauthorized use preventing device (30, 31) configured to prevent an unauthorized use of the electric lawn mower, wherein: the unauthorized use preventing device (30, 31) includes a key and a key receiver, and the key receiver is disposed on the mower body at a position proximal to the battery mount device, wherein: the unauthorized use preventing device comprises a lock mechanism including the key and the key receiver configured as a key insertion portion for locking and unlocking the electric motor; when the key is inserted into the key insertion portion, the electric motor is unlocked and can be started; the key insertion portion is disposed proximal to the battery mount device; the battery mount device includes a battery mount base and a battery cover; the battery mount base is disposed on the mower body and configured to be able to hold the battery; the battery cover is configured to be able to cover the battery mount base and can be opened and closed; characterised in that the key insertion portion is positioned so as to be covered by the battery cover when the battery cover is closed. the unauthorized use preventing device (30, 31) includes a key and a key receiver, and the key receiver is disposed on the mower body at a position proximal to the battery mount device, wherein: the unauthorized use preventing device comprises a lock mechanism including the key and the key receiver configured as a key insertion portion for locking and unlocking the electric motor; when the key is inserted into the key insertion portion, the electric motor is unlocked and can be started; the key insertion portion is disposed proximal to the battery mount device; the battery mount device includes a battery mount base and a battery cover; the battery mount base is disposed on the mower body and configured to be able to hold the battery; the battery cover is configured to be able to cover the battery mount base and can be opened and closed; characterised in that the key insertion portion is positioned so as to be covered by the battery cover when the battery cover is closed. the unauthorized use preventing device comprises a lock mechanism including the key and the key receiver configured as a key insertion portion for locking and unlocking the electric motor; when the key is inserted into the key insertion portion, the electric motor is unlocked and can be started; the key insertion portion is disposed proximal to the battery mount device; the battery mount device includes a battery mount base and a battery cover; the battery mount base is disposed on the mower body and configured to be able to hold the battery; the battery cover is configured to be able to cover the battery mount base and can be opened and closed; characterised in that the key insertion portion is positioned so as to be covered by the battery cover when the battery cover is closed.