A safety syringe has a barrel, a pushing element, a retracting element, and a needle group. The barrel is hollow and has a needle-group mounting end, an operating grip end, and a barrel lumen. The pushing element is retractably mounted in the barrel lumen and has a pushrod chamber. The retracting element is airtightly and slidably mounted in the pushrod chamber. The needle group is connected to the needle-group mounting end of the barrel. The present invention can pull the retracting element to move relative to the pushing element to form a low pressure condition in the pushrod chamber as a vacuum status. After the injection, a vacuum attraction force in the pushrod chamber can retract the used needle group into the pushrod chamber for safe use of the safety syringe.
