A trap for small noxious animals, such as mice, and comprising a holder (1) in form of a frame for holding a tightening element (3) in form of a shield. The trap (1) is arranged to be able to take a first, non-tightening position and at least a second, tightening position (12). The holder (1) shows a support (4) for a bait (20). The element (3), consisting of a sheet-metal, shows a setting-tongue (5) cut in the element (3), which tongue is arranged preloaded in the trap (1). In the said first position of the trap (1), the setting-tongue (5) is arranged at a distance from the support (4) and in the said second position (12) of the trap (1), an end portion (7) of the setting-tongue (5) is arranged to extend over the outer end (14) of the support (4) and touch the bait (20), while a second end portion (9) of the setting-tongue (5) is arranged to touch a stop in the holder (2). The trap (1) can be arranged in the said second position (12) or a setting-position by the fact that the element (3) is brought to take a bent position in the holder (2) and by that tightened and for the trap (1) releaseable position, whereby simultaneously the setting-tongue (5) is brought to touch the bait (20) and the said stop in the holder (2). During consumption of the bait (20), the setting-tongue (5) change position and when the setting-tongue has reached a predestinated position, the trap (1) release by the fact that the element (3) is strived to return to its said first position.