Purpose: This study analyzes service quality of Pivate Brand (PB) productsto provide some academic and practical implications. Research design, data, and methodology: The focus is on how service quality of No Brand, which has recently received much attention, affects brand attitude and, to confirm whether consumers' prior knowledge of PB moderates this effect. A total of 167 men and women in their 20s who have experience using No Brand were surveyed. Hypothesis was verified by using hierarchical regression analysis. Results: a) Tangibles, reliability, empathy, and assurance of service quality for No Brand have a positive effect on brand attitude; b) The moderating effect of prior knowledge is only statistically significant in the context of reliability. Conclusion: This study provides academic and practical implications for establishing differentiated PB strategies. It highlights the effects of service quality and consumer prior knowledge on brand attitude. This suggests that the sub-dimension of PB service quality has a discriminatory effect on the brand attitude of No Brand, and that consumer's prior knowledge of the product influences reliability of service quality. Therefore, consumer's prior knowledge is important in order to increase trust.