A positively chargeable toner includes toner particles each including a toner mother particle and an external additive adhering to a surface of the toner mother particle. The external additive includes first resin particles each having a surface to which a cationic surfactant adheres and second resin particles each having a surface to which an anionic surfactant adheres. Respective number average primary particle diameters of the first resin particles and the second resin particles are at least 60 nm and no greater than 100 nm. A detachment ratio of the first resin particles in a dispersion of the toner subjected to five-minute ultrasonic treatment is no greater than 20% in terms of a peak intensity percentage in a fluorescent X-ray spectrum plotted for the dispersion of the toner. A detachment ratio of the second resin particles in the dispersion is at least 30% and no greater than 60% in terms thereof.