PROBLEM TO BE SOLVED: To provide a liquid injection device capable of easily controlling cutting depth, and a medical instrument.SOLUTION: The liquid injection device includes: a liquid chamber 30 capable of changing a capacity inlet and outlet channels 30A and 30B which communicate with the liquid chamber 30 a capacity changing section 42 which changes the capacity of the liquid chamber 30 a liquid injection pipe 16 which is equipped with a liquid injection opening 28 and which emits a jet of liquid a cooling section 90 which cools gas and a gas injection pipe 18 which is disposed on the outer periphery of the liquid injection pipe 16, which is equipped with a gas injection opening 36, and which emits a jet of cooled gas cooled by the cooling section 90. In the liquid injection pipe 16, a guidance surface for guiding an injection direction of the cooled gas jetted from the gas injection pipe 18 is formed.COPYRIGHT: (C)2012,JPO&INPIT【課題】切断の深さを制御することが容易になる液体噴射装置及び医療機器を提供する。【解決手段】液体噴射装置は、容積が変更可能な液体室30と、液体室30に連通する入口流路30A及び出口流路30Bと、液体室30の容積を変更する容積変更部42と、液体噴射開口部28を備え、液体を噴射する液体噴射管16と、気体を冷却する冷却部90と、液体噴射管16の外周に配設され、気体噴射開口部36を備え、冷却部90によって冷却された冷却気体を噴射する気体噴射管18と、を有し、液体噴射管16は、気体噴射管18から噴射される冷却気体の噴射方向を誘導する誘導面が形成されている。【選択図】図1
