PROBLEM TO BE SOLVED: To provide a liquid injection device for sucking liquid injected from a discharge port, blood congested in a surgical site and cut biological tissues without sucking or damaging uncut tissues, while securing a necessary sucking amount.SOLUTION: The liquid injection device configured to cut biological tissues by injecting liquid from a discharge port 122 towards the biological tissues includes: a liquid injection means 100 for injecting liquid from the discharge port 122 as a pulsating flow and a suction means 150 for sucking at least either injected liquid or cut biological tissues by periodically varying negative pressure. The suction means 150 periodically repeats suction and suction stop. The suction means 150 sucks the tissues when the liquid is not injected from the discharge port 122.
