A replaceable blade utility knife is disclosed that uses permanent magnet to facilitate opening the knife handle for blade replacement. The utility knife has a handle made of two halves. The halves are held together by a connector, and rotate around the connector when the knife handle is opened. Permanent magnets are mounted in each half of the knife handle to separate the halves, rotate the halves to the desired open position, and to hold the halves in position while the blades are being changed. The permanent magnets act as a magnetic actuator for opening the handle halves.