Groundnut (Arachis hypogeae. L) is an important oil seed grown in over 100 countries for its nutritional value. In order to improve its storability and value, various ways of processing the seeds have been adopted among which is the roasting and removal of husk or rind from the roasted groundnuts. The process of removing of groundnut husk is mostly done manually and inappropriate for large scale processing. In order to improve groundnut seed husk dehulling process through mechanization, a roasted groundnut seed dehulling machine was developed and the effects of operating speed of the machine and moisture content of the seed on the on the efficiency of the machine was studied. 1kg of the roasted groundnut in five replicates with moisture content of 1.4, 1.6, 1.8, 2.0 and 2.2 % (w.b) respectively, was fed into the machine at different speed of 30, 35, 40, 45 and 50 rpm for each replicate. The machine had the best dehulling efficiencies of 80%, 78%, 77%, 90% and 73% at the lowest speed (30 rpm) while the lowest efficiency of 57%, 49%, 53%, 52% and 46% was recorded at the highest speed (50 rpm) in all moisture content (1.4, 1.6, 1.8, 2.0 and 2.2%) respectively. The best performance efficiency of 90% was gotten at 30 rpm and moisture content of 2.0 % (w.b). Hence, an optimum operating condition was established for the machine.