To properly calculate a residual quantity of a medium, in a printer using a roll-like medium.

This printer 10 uses the roll-like media 52a and 52b, and includes a medium holding roll 60 for holding the roll-like medium 52a, an ink jet head 14 being a printing part for printing on a medium 50 delivered in response to the rotation of the medium holding roll 60, a rotation detecting part for detecting the rotation quantity of the medium holding roll 60, a medium carrying quantity detecting part for detecting the carrying quantity of the medium 50 carried to the ink jet head 14, a medium thickness calculating part for calculating the thickness of the medium 50 based on the rotation quantity detected by the rotation detecting part and the carrying quantity detected by the medium carrying quantity detecting part, and a medium residual quantity calculating part for calculating a residual quantity of the medium 50 wound on a core 54 to the roll-like medium 52a based on the rotation quantity detected by the rotation detecting part, the carrying quantity detected by the medium carrying quantity detecting part and the thickness of the medium 50 calculated by the medium thickness calculating part.

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