PRINTING UNIT AND PRINTER

PROBLEM TO BE SOLVED: To provide a printing unit that prevents foreign matter such as a piece of paper from entering between a light receiving part and a light emitting part and that can suppress occurrence of erroneous detection, and to provide a printer.SOLUTION: A printing unit comprises: a holder 21 that can slidably move so as to freely approach a fixed blade and be separated from it; a movable blade held by the holder 21; and a sensor part 50 that detects an operation of the holder 21. The sensor part 50 comprises: a pair of wall parts 50A, 50B fixed to a holder housing 15 accommodating the holder 21, and arranged oppositely to each other with a space between them; a light emitting part 51b provided on the one wall part 50A; a light receiving part 51c provided on the other wall part 50B; an inserted piece 52 provided to the holder 21, inserted between the one pair of wall parts 50A, 50B, and intercepting detection light B emitted from the light emitting part 51b toward the light receiving part 51c; and pressing members 55, 55 provided to the holder 21 and pressing a fine piece of paper Ps on both outer sides of the pair of wall parts 50A, 50B.SELECTED DRAWING: Figure 7 【課題】受光部と発光部との間に紙片等の異物が入り込むのを防止し、誤検知の発生を抑えることのできる印字ユニットおよびプリンタを提供する。【解決手段】固定刃に対して接近離間自在にスライド移動可能とされたホルダ２１と、ホルダ２１に保持された可動刃と、ホルダ２１の動作を検出するセンサ部５０と、を備え、センサ部５０は、ホルダ２１を収容するホルダハウジング１５に固定され、間隔を空けて対向配置された一対の壁部５０Ａ，５０Ｂと、一方の壁部５０Ａに設けられた発光部５１ｂと、他方の壁部５０Ｂに設けられた受光部５１ｃと、ホルダ２１に設けられ、一対の壁部５０Ａ，５０Ｂ間に挿入されて、発光部５１ｂから受光部５１ｃに向かって発光される検出光Ｂを遮る挿入片５２と、ホルダ２１に設けられ、一対の壁部５０Ａ，５０Ｂの両外側において細片Ｐｓを押さえ込む押さえ部材５５，５５と、を備える。【選択図】図７