A bill processing machine according to the present invention includes an element array portion and a light guiding member. The element array portion is arranged so as to face one side of a conveyance path of a bill, and includes a light receiving element group, a light emitting element and an other side light receiving element. The light receiving element group includes a plurality of light receiving elements, and an arrangement direction of the light receiving elements is perpendicular to a conveyance direction of a bill. The light emitting element is arranged on one side of the arrangement direction of the light receiving elements. The other side light receiving element is arranged on an other side of the arrangement direction of the light receiving elements. The light guiding member is arranged opposite to the element array portion with respect to the conveyance path so that the light guiding member and the element array portion sandwiches the conveyance path therebetween. The light guiding member includes a first refracting portion, a second refracting portion and a main body portion. The first refracting portion refracts irradiated light of the light emitting element in a direction parallel to the arrangement direction. The second refracting portion refracting the irradiated light refracted by the first refracting portion toward the other side light receiving element The main body portion diffuses in an approximately uniform manner the irradiated light refracted by the first refracting portion toward the light receiving element group.