In recent years, men's shirts have become diversified in terms of quality, purpose and way of wearing, while the higher quality of life has created stronger fashion-consciousness. This paper investigated the situation and causative factors behind the improved quality of men's shirts, judged from the relationships between wearers and the living environment. Using data from general and trade newspapers and statistics for production and consumption, the historical development of shirts over the last three decades was examined to clarify the factors underlying their quality improvement. The following factors for the quality improvement of shirts could be found in the changes in the living environment which affect people's inner and outer lives and in the consumption and marketing of ready-made shirts. 1. Changes of Life Environment : 1) Air conditioning has changed the conception of shirts from practicality to fashionableness. 2) Increasing leisure time has separated leisure shirts from business shirts. 2. Quality : 1) Since the 1960s, manufacturers have improved the quality of ready-made shirts in terms of materials, tailoring and sizes. 2) Since the 1970s, consumer preference for quality has strengthened and the proportion of non-white shirts, i.e ., colored, patterned and fancy shirts, has risen. 3) On the suppliers' side, with profitability deteriorating every year and developing countries growing more competitive, manufacturers are producing enhanced products while retailers are upgrading their merchandise and the atmosphere of their stores.