The utility model relates to a friction force demonstrator in the field of teaching instruments. The friction force demonstrator comprises a left working part, a right working part and a middle working part arranged between the left working part and the right working part, The left working part and the right working part are directly fixed on the support frame; A front rotating roller and a rear rotating roller are arranged at the front end and the rear end of the middle working part respectively, a friction working face is arranged between the front rotating roller and the rear rotating roller in a surrounding mode, and a rotating device is arranged on the front rotating roller or the rear rotating roller. The friction working face comprises a plurality of component working faces which are spliced end to end in sequence; A friction block is arranged on the friction working surface; The front end of the supporting frame is provided with a driving working part corresponding to the friction block, and a dynamometer is arranged between the driving working part and the friction block; The experimental device can simultaneously simulate the friction force of experiments under differentroughness environments, is convenient for students to operate and practice, improves the cognition degree of the students, and improves the teaching quality at the same time.