To provide an insole having versatility to be applied to various kinds of shoes and having a projection for preventing forward slip, wherein the shape of the projection has few risks of giving a sense of disorder to feet when used.

An insole 0101 includes: a base 0102 in contact with at least part of a sole; and a projection 0103 that can be used by being held between a big toe 0105 and an index finger 0106 of a foot, wherein a main shape of the projection 0103 as observed from a cross section approximately parallel to the base 0102 is vertically long such that the horizontal direction length of the foot 0104 is shorter than the longitudinal length connecting the heel side and the toe side of the foot, and is a teardrop shape narrowed toward the toe side of the foot.