To provide a printer storing a sheet having been printed by a printing means in a storing section once in which sheets fed to the storing part by a conveying means are accurately detected while discriminating the same one by one.

The printer having a printing means 3 for printing the sheets, a sheet storing section 4 for storing a plurality of sheets P having been printed by the printing means 3 with the same overlapping each other, the conveying means 7A for conveying the sheets P having been printed from the printing means 3 to the sheet storing section 4, and a sheet moving means 41 for moving the sheets P conveyed to the sheet storing section 4 in a sheet overlapping direction, is equipped with a reflecting type optoelectric sensor S3 arranged in a direction for irradiating detecting light to the sheets P during conveying and to the sheets P in the sheet storing section 4 and a signal processing section for receiving the output signal of the optoelectric sensor S3 and for generating sheet detecting signals showing the sheets P while discriminating the same one by one based on the level change of the signals accompanied by the movement of the sheets P.