The purpose of the present study was: 1) to investigate the effects of two types of comparative advertising--Merit-type (emphasizing positive aspects of their own brand) and Demerit-type (pointing out negative aspects of the rival brand); and 2) to find an effective strategy against comparative advertising of a rival company. Subjects were shown advertisements, and were then asked to evaluate those advertisements (17 items), the brands and company images (3 items) for these two companies. The results are as follows: Comparative advertising, especially of the Demerit-type, was the most conspicuous type of advertising, which also had a significant negative effect on the perception of rival brands. However, this type of advertising also had a negative effect on his own advertising, the brands advertised, and the company itself. Furthermore, it was found that when a rival company uses Demerit-type advertising, it is better not to respond by the same type, but to respond by Merit-type advertising. In such a situation, positive image of his own brand and company become significantly higher.