A bicycle frame has a front frame, a lower bracket assembly, an upper bracket assembly, a rear frame and a shock absorber. The front frame has a head tube, a down tube, a bottom bracket shell and seat tube. The lower bracket assembly is connected pivotally to the bottom bracket shell and has a lower connecting bracket. The upper bracket assembly is connected pivotally to the seat tube and has two upper connecting brackets. The rear frame is connected pivotally to the upper connecting brackets and the lower connecting bracket of the upper and lower bracket assemblies and has an upper fork, a lower fork and two dropouts. The shock absorber is mounted pivotally between the upper connecting brackets and the lower connecting bracket.