Abstract: The disposable lancet device has a casing, a lancet assembly, a spring and an actuator is provided. The casing is hollow and has a front end, an open rear end, two inner side surfaces and two converging inner linear surfaces. Each inner linear surface has a shoulder and an inclined limit. The lancet assembly is mounted slidably in the casing and has a longitudinal hub with two resilient tabs that abut the shoulders and a needle cap. The spring presses against the longitudinal hub. The actuator presses against the spring and has a pushbutton assembly and two actuating tabs that press against and release the resilient tabs from the shoulders. The needle is retracted by the resilient tabs pressing against the inclined limits. Therefore, the used needle will not protrude from the casing to prick a user cannot be used again.