In industrial fields, arm strength supporting devices for workers have been developed to improve work efficiency and prevent injuries caused by muscle fatigue during repeated tasks. A device supporting arm strength based on an adjustable counterbalance mechanism with no motor or sensor has been previously developed, but it had a disadvantage in that the compensation torque adjustment is difficult during the tasks. To solve this problem, we suggest a mechanism which can easily adjust the compensation torque by using a spring-latch module. The adjustable counterbalance-based arm strength supporter (ACASS) using a spring-latch module provides two compensation torque modes which can be switched with simple shoulder movements. The muscle strength was measured by electromyography sensors to verify the performance and convenience of the ACASS. It is shown that the switching of compensation torque of the proposed ACASS is much faster and easier than that of the previous devices.