A needle device includes a shell, a needle unit and an actuator. The needle unit includes an outer needle guide and a needle member. The outer needle guide has a piercing end for penetrating into a biological body part. The needle member is disposed in the shell and the outer needle guide, has a needle tip protruding from a front end of the shell and is movable relative to the shell and the outer needle guide. The actuator is responsive to a control signal to drive the needle member and move the needle tip between a protruding position, where the needle tip protrudes out of the piercing end of the outer needle guide, and a retracting position, where the needle tip is retracted back into the outer needle guide.
