PURPOSE: To detect deformation and breaking of an outer blade even while the blade is in use, including an outer-blade pattern area where shaving is actually performed.

CONSTITUTION: An electrically insulating film is formed on the surface of an outer blade base material 1. On the electrically insulating film a conductive material 3 which detects deformation of the outer blade from changes in the electric resistance of the electrically insulating film is formed in one part of an outer-blade pattern area R and used as an outerblade deformation detecting portion 4. The conductive material 3 is formed on the electrically insulating film 2 and inside or outside the outer-blade pattern area R, and used as a transmitting portion 5 by which the result of detection of outer blade deformation by the outer edge deformation detecting portion 4 is transmitted to a predetermined portion.