A lancet pricking device comprises a lancet, a launching spring, a trigger part and a holder housing the lancet, launching spring and trigger part. The lancet comprises a lancet body, lancet cap and pricking needle. The pricking needle is in both the lancet body and lancet cap. The trigger part has a pair of arms positioned inside the holder. The launching spring is attached to the lancet body. The lancet body is secured to the arms of the trigger part by an abutment of the lancet body on the arms such that the launching spring is compressed before a pricking operation. The trigger part cannot be pushed toward the inside of the holder before the lancet cap is removed, but can be pushed toward the inside of the holder after the cap is removed. The lancet body warps when pressed to release the secured lancet body.