The present invention addresses the problem of providing a method for producing metal microparticles in which the particle diameter and the coefficient of variation are controlled. Using at least two kinds of fluid to be processed including a fluid which contains at least one kind of reducing agent, the fluid to be processed is mixed in a thin film fluid formed between at least two processing surfaces, at least one of which rotates relative to the other, and which are disposed facing each other and capable of approaching and separating from each other, and metalmicroparticles are separated. At this time, the fluid to be processed containing one or both of the fluid which contains at least one kind of metal and/ or metal compound and the fluid which contains at least one kind of reducing agent contains a water-containing polyol in which water and a polyol are mixed, and does not contain a monovalent alcohol, and the particle diameter and coefficient of variance of the separated metal microparticles is controlled by controlling the ratio of water contained in the water-containing polyol.