A speed change mechanism includes a housing (10), a guiding disc (20), a plurality of rolling columns (30), an input shaft (40), an output disc (50), and plural sleeves (60). The housing (10) includes an orifice (11), the guiding disc (20) includes a connecting hole (21), a plurality of notches (22), and the plurality of rolling columns (30) equidistantly arranged and fixed in the plurality of notches (22). The input shaft (40) includes a first stem (41), a second stem (42), and a cam (43), the output disc (50) includes an aperture (53), an output shaft (51), and plural posts (52). The plural sleeves (60) are fitted on the plural posts (52) and between the housing (10) and the plurality of rolling columns (30), and the plurality of rolling columns (30) abut against the cam (43), such that when the input shaft (40) rotates, it drives the plurality of rolling columns (30) to rotate.
