An air compressor more reliably protects a battery pack without lowering its operability for attachment to and detachment from a battery mount. The air compressor includes an electric motor driven on power from a battery pack having six faces, an operation unit operable to connect or disconnect power to the electric motor, an compression unit driven by the electric motor to produce compressed air, a tank that stores the compressed air, a battery mount that receives an attachment face of the battery pack, and a guard defining a protective area to contain the battery pack and the compression unit. The battery pack is attachable to the battery mount with at least three of the six faces exposed.