Abstract: The present invention discloses an adjustable dumbbell, comprising a dumbbell bar, wherein the dumbbell bar comprises a rotatable handle having a support plate fixed at each end thereof, and the support plate is connected to a locating plate on which a plurality of sets of pin holes are formed; a weight plate holder, in which a pin cartridge is mounted, is arranged on an outside of the locating plate, heads of the locating pins are arranged correspondingly to the sets of pin holes on the locating plate, U-shaped separation ribs of the weight plate holder are plugged each to each between two adjacent weight plates of weight plate sets at both ends, and the weight plates of each weight plate set are arranged in a plurality of arc-shaped grooves of the base. According to the adjustable dumbbell, all the weight plates are placed on the base and may be attached or detached without manual removal, and the lifting weight can be adjusted only by rotating the handle.