A toner is provided which is excellent in low-temperature fixability and offset resistance, has a wide fixing temperature range, provides fixed images with high gloss, and can form toner images having high quality. The toner is composed of toner particles having toner base particles each containing a binder resin and a colorant. When the viscosities of each of the toner particles measured at 100° C. and 110° C. by a flow tester heat-up method are represented by η100 (Pa·s) and η110 (Pa·s), respectively, an average variation in viscosity AηT represented by the following equation (1) satisfies the relationship of 0≧AηT≧−0.064: AηT=(log(η100)−log(η100)/(110−100)  (1); and η100 is 15,000 to 40,000 Pa·s.