To provide a locking screw preventing a general user from loosening a screw with an ordinary tool or the like after fastening the screw.

This locking screw is provided with a trim head 12 formed at the end of a screw part 11; a screw driving action head 14 spaced from the trim head 12 and having an engaging part 17 with the tool to engage the tool when fastening a screw part 11; and a connecting part 13 integrating the screw driving action head 14 and the trim head 12. The connecting part 13 is broken or the like when turning force of a predetermined value or more is applied to the connecting part 13. Consequently, safety is excellent because of preventing disassembly of equipment by loosening the screw 10 fitted to the equipment and avoiding an accident or the like caused by a user touching the equipment or a device with a possibility of danger.