A friction-roller speed changer has three intermediate rollers (12a, 12b, 12c). Two rollers (12a, 12b) of which act as a wedge roller and can be moved into the narrower area of an annular space (10) by the transmission of power, wherein during power transmission from the input side in the normal state to the output side. The other intermediate roller (12a or 12b), which does not act as the wedge roller, moves into the wider area of the annular space (10) against the elastic force of the spring (14) whereby transmission efficiency for bidirectional rotation is maintained while preventing backflow of power.