A magnetic one-component toner includes toner particles each including a toner base particle and an external additive attached to a surface of the toner base particle. The external additive includes conductive particles with a specific resistance of 1.0E+4 [.Math.cm] or lower, resin particles with a number average primary particle sizes of 50 nm or more but 100 nm or less, and silica particles. The resin particles are formed by using an anion surfactant and formed from a vinyl resin having a repeating unit represented by general formula (1) below, a repeating unit represented by general formula (2) below, and a repeating unit derived from a sulfo group-containing vinyl compound. A content ratio of the repeating unit derived from the sulfo group-containing vinyl compound in the vinyl resin is 2.0 mol % or more but 5.0 mol % or less relative to all repeating units in the vinyl resin.

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