An electronic device comprises a casing, an electronic element, and an ejection mechanism. The casing has a receiving space and an opening. The ejection mechanism includes: a holder for holding and carrying the electronic element to pass through the opening to be exposed outside the casing; a first biasing spring biasing the holder to project outwardly from the opening; a stopping member rotatably pivoted to the casing and contactable with a projection of the holder; a second biasing spring biasing the stopping member to contact the projection, and having an elastic modulus greater than that of the first biasing spring; and a releasing member operable for driving the stopping member to detach from the projection.