To provide a film unit with a lens constituted so that information can be accurately transmitted by alternatively erasing magnetic data previously recorded on photographic film by a permanent magnet.

This film unit with a lens 2 in which the photographic film 23 on which the magnetic data is recorded by every frame is previously loaded at the manufacturing time is equipped with a magnetic data erasing mechanism 61 for erasing the magnetic data, a switching knob 64 switching whether or not the magnetic data is erased, and an automatic winding device utilizing the elastic energy of a coil spring 70. The erasing mechanism 61 is provided with the permanent magnet 62. The magnetic data is erased by consecutively winding the film by one frame without stopping the film midway by the automatic winding device in a state where the magnet 62 approaches to a position closer to a cartridge chamber 22 than the top side end of a magnetic data recording area 53 by the knob 64.