An angle-adjustable supporting mechanism that includes a knob-type locking mechanism and a rotatable holder is provided. The knob-type locking mechanism has a base, a knob, and a latch member. The base has a receiving space and a supporting portion. The knob is rotatably received in the receiving space. The latch member is movably received in the supporting portion in a linear direction. The latch member has a bolt, a first stressed part, and a second stressed part. The bolt is disposed at one side of the first stressed part. The first stressed part is disposed between the bolt and the second stressed part. When the knob is rotated in different directions, the bolt of the latch member is drove to lock or release.