Abstract: A paper advance mechanism which minimizes the size of a printer includes a printer head and a platen disposed below the printer head and separated from the printer head by a gap. A first channel defined by the platen and a chassis is in the form of an arc for guiding a sheet from a paper cassette to advance along the chassis and towards the printer head while the platen is rotating in a first direction. A pair of driving rollers is disposed close to the gap for controlling the moving direction of the sheet. A second channel in communication with the first channel guides the sheet from the first channel, and a third channel in communication with and horizontally aligned with the second channel guides the sheet from the second channel to a paper exit opening. The printer had prints on the sheet when the sheet is advancing from the second channel to the third channel. After printing is finished, the sheet is fed back to the second channel for retrieval.