The purpose of this study is to investigate the user characteristics in different age groups by investigating the level of satisfaction and preference of design and function of mobile phone. 160 subjects participated in the experiment. Subjects with different ages were selected and divided into four groups: young age group (20 to less than 45), $1^{st}$ middle age group (45 to less than 55), $2^{nd}$ middle age group(55 to less than 65), and elderly group(over 65). A questionnaire was developed based on the previous design guideline, and additional questions were made to test newly developed function and design of the mobile phone. In particular, depth interviews were conducted in order to have a proper response from old subjects who have difficulties in completing written questionnaire. In result, it was found that except for price the major criterion to purchase mobile phone was the design, and the function of phone was the next except for elderly group. In the case of elderly group, the screen size is the first. Statistical results indicated that 37.5% of the young age group, 22.5% of $1^{st}$ middle age group, 22.5% of $2^{nd}$ middle age group and 10.0% of the elderly group preferred the design to function when they purchase mobile phones. Most elderly people were not satisfied with the supplementary function of the mobile phone. The $1^{st}$ middle age group did not know exactly how to use the supplementary service although they were willing to use it. Regarding the emotional preference on the type of phone, the sliding type was preferred most. Current results can be used to anticipate the future trend of mobile phone and design a user-friendly product for the aged population.