The invention relates to a trap with vertical flap which allows the passage in only one direction, being closed by its own weight, and to a manner of using the same, the trap being meant to catch mice, rats or small animals living near human communities to which they can transmit diseases, parasites or produce material damages. The claimed trap comprises an enclosure () provided with a way () of access, inside which there is mounted the flap () fixed in a hinge () by means of an axle (), about which the flap () can rotate inside the enclosure () shuttering or clearing the way () of access, the flap () consisting of a small half-flap () and a large half-flap () coupled to each other by means of the axle () of the half-flap, a stopper () and a blocking apron (). The manner of using claimed by the invention consists in placing the bait into the enclosure () where the animal enters by pushing the flap () which rotates about the axle () thereof clearing the way () of access, after the entrance of the animal, the flap () being closed by its own weight and, if the animal intends to get out it will actuate the large half-flap () which pushes the small half-flap () by means of the axle (), said small half-flap will slide down on the stopper () below the blocking apron (), the animal remaining captured.
