PT. XYZ is an electrical machinery repair services company. The amount and density of operator activity can affect worker fatigue. This research conducted to calculate the level of physiological and psychological workloads and ideals rest periods for operators in the Mechanical Department of PT. XYZ. The method to calculate physiological workload is direct measurement by measuring heartbeat, whereas the method to calculate psychological workload is NASA-TLX Method. The results show that the most severe physiological workload experienced by Mr. Nur who is a medium-sized lathe operator with a value of energy consumption of 8.497 Kcal/minute before a break and 7.602 Kcal/minute after a break, the ideal rest time for Mr. Nur is 112 minutes with work duration from 07.00-12.00 WIB and 66 minutes with work duration from 13.00-16.00 WIB, while Mr. Supardi and Mr. Didik requires a rest time of 103 minutes and 38 minutes with work duration from 07.00-12.00 WIB and the level of psychological workload for the 12 operators are high and very high. Therefore the company can minimize the level of physiological and psychological workload by calculating the workload of the operator in a balanced manner.