An instrument support has a bracket provided with a first leg, a second leg, a disk and two forks. Each of the first leg and the second leg has a through hole defined in a side face of the first leg and second leg to communicate with an interior of the first leg and second leg to receive therein a spring-ball combination. A fork is movably and respectively received in the first and second legs and has an adjustable rod integrally formed with the fork and having recesses defined in a side face of the adjustable rod to correspond to the spring-ball combination so that movement of the two forks provide adaptation to thickness of different instruments.