A reinforcing film comprises a pressure sensitive adhesive layer laminated and fixed on a principal surface of a film substrate. The pressure sensitive adhesive layer is formed of a photocurable composition containing a photocurable agent and a base polymer having a crosslinked structure. A frictional force of the pressure sensitive adhesive layer measured with a frictional force microscope at a frequency of 5 Hz is preferably 2 to 5 times a frictional force at a frequency of 0.1 Hz. After photocuring of the pressure sensitive adhesive layer, a frictional force of a photocured pressure sensitive adhesive layer measured with the frictional force microscope at a frequency of 5 Hz is preferably not less than 5 times a frictional force measured at a frequency of 0.1 Hz.