An animal trap device comprises a base, a circular cover plate, an elastic element and an elastic lasso. The circular cover plate comprises a top portion, a surrounding portion; wherein the surrounding portion surrounds a circumference of the top portion. The top portion has a support disc and at least one flange protruding from a side surface of the support disc. The elastic element is configured between the base and the circular cover plate, and adapted to provide the top portion with an upward elastic force. The elastic lasso is wound around the surrounding portion, and positioned below the at least one flange. The elastic lasso will be blocked by the at least one flange and the surrounding portion, retained in open position until leaving the surrounding portion when the top portion is exerted with a force to move downward.
