The present invention provides a rat trap device, which comprises: a cage including a cage body defined therein an opening, and a door plank for selectively closing the opening； an elastic element having one end fixed to the cage body and the other end fixed to the door plank； a linkage member pivoted to the cage body, wherein one end of the linkage member selectively abuts against the door plank； and a movable member pivoted to the cage and distant away from the opening, and including a first hook part and a second hook part opposite to each other, wherein the first hook part is disposed in the cage body and the second hook part selectively hooks the other end of the linkage member that is opposite to the end abutting against the door plank. Therefore, when the bait is hanged inside the cage body and is distant away from the first hook part of the opening, a rat can bite the bait only if its whole body is inside the cage body, thereby preventing the trapped rat from moving with the rat trap device after trapped by the rat trap device.本創作捕鼠器具有：一籠子，其包含一籠體，其形成有一開口；及一門板，門板選擇性地封閉開口；一彈性元件，其一端固設於籠體，另一端固設於門板；一連動件，其樞設於籠體，且其一端選擇性地抵靠於門板；以及一活動件，其樞設於籠體上且遠離開口，並具有相對的一第一勾部及一第二勾部，第一勾部位於籠體內，第二勾部選擇性地勾住連動件相對於抵靠門板的另一端。因此，將餌食懸掛在籠體內且遠離開口的第一勾部，因此老鼠必須整個身體都位在籠體內才能咬取餌食，而可避免捕獲後老鼠帶著捕鼠器移動。
