A golf bag cart foldable device includes a bottom cart stand having a link segment at its top, where both sides of the link segment each is in pinned connection with a rear wheel frame, which has its bottom end join the rear wheel, and the bottom cart stand is provided with a slider at the bottom of the link segment. An upper cart stand is in pinned connection with the link segment at its bottom, and has a bracket at its top, where the bracket couples to a mount at its one end. A handle bar is joined the mount at its bottom at which an angle adjustable joint is located, and has a score board at its top. A linkage set comprises a first linkage being set up between the upper cart stand and the slider, a second linkage being set up between the slider and the rear wheel frame, and a third linkage being set up between the mount and the first linkage. Through the linking of the linkage set, the angles between the upper cart stand and the handle bar and between the bottom cart stand and the rear wheel frame will change for the folding or fixing of the device.