Abstract: An umbrella frame includes a runner movably sleeved on a central shaft and a rib-and-stretcher assembly coupling the runner with a top end of the central shaft for spreading and collapsing a canopy. A plurality of petal-like members extend radially and axially from each of the top end of the central shaft and the runner, and define a plurality of accommodating slots for pivotally receiving a plurality of modular connector shells. Each of the rib unit and the stretcher unit has a plug-like connecting end configured to be fitted in a socket-like connected end of the corresponding connector shell and detachably fastened by a fastener. The rib-and-stretcher assembly can be conveniently and easily connected to and detached from the central shaft for replacement.