The purpose of this study is exploratory investigation of safety and efficacy (dose response and optimal dose according to the percent reduction from baseline in serum urate level at the final visit) of FYU-981 administered orally to hyperuricemic patients with and without gout for 8 weeks (dose-escalating initial period: 4 weeks followed by maintenance period: 4 weeks) by the method of randomized (dynamic allocation), placebo-controlled, double-blind, parallel group comparison.