PROBLEM TO BE SOLVED: To provide a passage prevention fence of a small animal in which the need for providing a climbing prevention fence of the small animal such as a cat in garden trees is eliminated and production cost can be reduced.SOLUTION: Plate materials 4 for making claws of a small animal such as a cat be impossible of catch are overlapped on one fence side and other fence side of the upper part of a fence 3, respectively. An upper end 4J of these pair of plate materials 4 is projected upward from the upper side frame 7 constituting the upper end of the fence 3, so that the claws of the small animal is made impossible of the catch. Also, a cylindrical member 5 with a diameter larger than the length between surfaces of the surface side of the pair of plate materials 4 is placed and fixed to the upper side frame 7 along the upper side frame 7. Then, an outer circumferential surface of a lower half part of the cylindrical member 5 is placed on the upper end 4J of the pair of plate materials 4, and is supported from the lower part to the pair of plate materials 4.SELECTED DRAWING: Figure 2【課題】庭木にねこ等の小動物の登り防止柵を設ける必要がなく、製作コストを低減できる小動物の通過防止柵を提供する。【解決手段】ねこ等の小動物の爪が引っ掛かり不可能な板材4が、柵部3の上部の一方の柵面と他方の柵面にそれぞれ重ね合わされており、これら一対の板材4の上端4Jは、柵部3の上端部を構成する上側枠7よりも上方に突出し、小動物の爪が引っ掛かり不可能で、かつ、一対の板材4の表側の面同士の間の長さよりも大径の円筒部材5が、上側枠7に沿ってこの上側枠7に載置され固定されるとともに、円筒部材5の下半部の外周面が一対の板材4の上端4Jに載置されて一対の板材4に下方から支持されている。【選択図】図2