This study aims to explore the career transition experience and process of middle-aged male office workers subjected to involuntary retirement, an effort to further develop a substantive theory on the career transition experience. Research data were collected mainly through in-depth interviews and the grounded theory was adopted. The selection process followed the theoretical sampling method, and eleven middle-aged male participants were selected from those who had held an office work position for more than ten years at their main job, and who were between forty and sixty four years old. This study developed 116 concepts, 54 sub-categories, and 20 categories. The central phenomenon of the career transition of involuntary middle-aged male retirees from office work was 'crushed by the pressure of retirement.' The chronological process of career transition involves five stages: searching directions, moving, accepting, continuing, and stop and thinking. The core category was 'to be satisfied with the work itself without dwelling on the past self'. Therefore, the findings of this study are expected to contribute to understanding retirement and career transition experience of middle-aged men from a new perspective in homes, organizations, society, nation, and counseling field, and to be utilized as a foundation for career transition policy, training, and counseling intervention.