This research aims to shed a light on the benefits and perceived risks to the willingness to use perceived by consumers, centering on design-customizing service catering to individuals’ tastes and needs, and to study their impacts on the use of a design-customizing service. The validation of how benefits and perceived risks affect the intention to use showed that only aesthetic and self-expressive benefits had significant impacts on the willingness to use. However, only time/economic loss and self-design risks had negative impacts on the willingness to use a service. By gender, there was no difference in benefits and perceived risks to willingness to use for the benefit factors, whereas in terms of perceived risks to willingness to use factors. By age, there were also differences in the effects of benefits and perceived risks to purchase on the willingness to use a rash guard customizing service. There were variations in the perceived risks to the willingness to use and benefits depending on age. In particular, it was found that there were no perceived risks to the willingness to use for the age group of 10s. As design-customizing services based on individual tastes have drawn more attention recently, this research on the benefits and perceived risks to purchasing a rash guard design customizing service, as well as their effects on service use (particularly backed up by comparative analysis by gender and age), is expected to provide insights into design-customizing service strategy development.