This research is a case study at PT Surya Toto Indonesia, a company engaged in the production of sanitary goods. Lot of activities in this company are done manually.  The ages of the workers in assembling section range from 19 to 48 years old. The purpose of this study is to determine the relationship between the age of workers and the mental workload of workers in assembling difficult type products. This cross-sectional study was conducted in 2019 on 73 workers who participated in this study by filling out a NASA-TLX mental workload questionnaire. The results showed that assembling difficult type products had a high mental workload and mental workload of the middle age group is 7.5% higher than the young group. An analysis of the 6 NASA-TLX dimensions showed that effort was the mental load that most affected in both age groups due to monotonous work, high concentration levels, and musculoskeletal symptoms as a result of repetitive work. ANOVA showed that there was no effect of age on the 6 dimensions of mental workload of the assembling workers. The main source of mental burden for workers in assembling products is the behavior characteristic

Keywords

Mental, Workload, High Difficulty Assembling, NASA-TLX.