Tasks involving the thumbs of workers are frequently carried out at industrial sites or in laboratories. This study measured thumb endurance time according to relative force levels in males and females. The experiment in this study involved 30 healthy participants (15 males and 15 females). Maximum thumb pressing force (MTPF) was measured and thumb endurance curves were developed using the measured thumb endurance time of participants’ dominant hand according to various force levels (10, 20, 40, 60, 80, and 100% MTPF). On the basis of the results, females demonstrated greater endurance time than males at 20% MTPF, and statistically significant differences according to gender are not shown at MTPF levels of 40% or higher. A rapid increase in endurance time was observed at low force levels. The findings of this study are expected to facilitate the establishment of appropriate working levels for the thumbs of workers in order to optimize work design. In this study, the effects of gender and target force level on thumb endurance time performance were evaluated. The findings of this study could provide valuable information for developing ergonomic guidelines of thumb pressing force tasks for the workers.