A bicycle-fork support device configured to hold: a conventional fork, allowing insertion of a quick-release-skewer support shaft, in a lower end portion of the fork of a bicycle; a through-axle fork where a through-axle insertion hole for securing a through-axle hub formed in a lower end portion of the through-axle fork, and configured to deal with outer diameters of through-axle forks. The support-fork switching unit includes: a support-device main body where a hollow portion is formed; end portions formed in right and left end portions of the hollow portion; a conventional-fork-use supporting body including, a contacting portion formed with an internal shape that fits the support shaft; a through-axle-fork-use supporting body including, a contacting portion formed with an internal shape that fits the through axle; and a unit for removably mounting any of the supporting bodies on the right and left end portions.