An office chair allowing removing and mounting of massaging mechanism comprising a seat pad, a back-rest chair pad, a left armrest and a right armrest. There is a cavity inside the back-rest chair pad a massaging mechanism is fitted inside the cavity the massaging mechanism comprises a massaging head assembly and a driving assembly, both of which are mounted on a bottom case. The back-rest chair pad is furnished with at least 1 pair of rotary knobs. When the massaging mechanism is fitted inside the cavity and the rotary knobs rotate, press against the bottom case, and retain the massaging mechanism inside the cavity. To take out the massaging mechanism, just rotate the rotary knobs, and take out the massaging mechanism out of the cavity. The massaging mechanism may be replaced for various massaging effects that may relieve fatigues caused by sedentariness.
