A protector with a sensor is installed on a sliding door (1) for detecting an alien substance by touch between two conductive parts (54, 55) in a hollow part (52) with a space (53) therebetween. An outer peripheral surface of the hollow part is an outer coat (52a) substantially having a horseshoe shaped cross section. Both ends (52b, 52c) of the outer coat are connected with an installation base member (11). The two conductive parts (54, 55) comprising a conductive part (55) having a convex shape on a lower part of the hollow part and a conductive part (54) having a concave shape on an upper part of the hollow part are shaped and positioned in a manner that the space (53) substantially has a V-shaped cross section and a uniform width in cross section, an opening of the V-shaped cross section faces a side of said installation base member, and both ends (53a, 54b) of the V-shaped cross section are continuously provided on an inner surface of the outer coat (52a).