A developer set includes a first developer and a second developer. The first developer contains a first toner containing first toner particles and a first carrier containing first carrier particles. The second developer contains a second toner containing second toner particles and a second carrier containing second carrier particles. The first toner particles and the second toner particles each include a toner mother particle and external additive particles attached to the surface of the toner mother particle. The external additive particles include spacer particles. The spacer particles have a number average primary particle diameter of at least 32 nm and no greater than 145 nm. The first carrier particles each include a first carrier mother particle and strontium titanate particles attached to the surface of the first carrier mother particle.