Designers are expected to create beautiful and functional products. Based on a concept of user-friendliness, users expect to understand functions mounted on a product without special knowledge and experience with the manipulation of the designers' real product, while usability of products is measured in terms of users' observation and manipulation. The purpose of this study was to focus on users' observation and to examine whether users can correctly understand functions of a designed product (digital sphygmomanometers), regardless of their medical knowledge, without manipulation. We conducted two experiments to test whether users, regardless of their expert knowledge, elicit high marks in the function-estimation task as well as in the beauty-evaluation task. Two groups of students with or without nursing education were asked to estimate functions and evaluate beauty of two types of digital sphygmomanometer (an old design model and its new model redesigned) based solely on the observation of the products' pictures without manipulating the real products. The results indicated that the two groups of participants showed higher correct responses to the old type than the new type in the function-estimation task, while they showed higher evaluations of the new type than the old type in the beauty-evaluation task. In particular, the results of nursing students in the function-estimation task indicated that medical knowledge in the nursing group did not contribute to the correct estimation of the operation procedure for the new model. These results suggest that designer's efforts for the new model were successful in production of beauty but were not successful in production of perceptive functionality under the present observation condition without manipulation of the real products. We discussed these results based on a framework of co-existence of beauty and functionality in the designers' work.