A method for producing a microparticle characterized in that the method comprises at least two steps as follows: a first step of forming a seed microparticle in a thin film fluid formed between at least two processing surfaces, a first processing surface and a second processing surface, which are disposed in a position they are faced with each other so as to be able to approach each other by using a surface-approaching pressure applying mechanism to apply a surface-approaching pressure, and to separate from each other by a separating force caused by viscosity and the pressure of the fluid, and maintaining the distance between the at least two processing surfaces at a predetermined minute distance by the balance between the surface-approaching pressure and the separating force, and where at least one of the processing surfaces rotates relative to the other, wherein in the first processing surface a groove-like depression extends in a radial direction and between the front edge of the depression and the outer peripheral edge of the first processing surface is formed a flat surface not having the depression, wherein a first fluid of the thin film fluid is introduced into between the processing surfaces, and a second fluid of the thin film fluid is introduced into between the processing surfaces from a separate path that is independent of the flow path introducing the first fluid and the second processing surface has an opening leading to between the processing surfaces, the opening being arranged in the second processing surface at a position opposite to the flat surface of the first processing surface such that mixing of the thin film fluid and formation of the seed microparticle is effected under laminar flow, whereby discharging a fluid which contains the seed microparticle in the process of growth thus formed as a discharge fluid from between the processing surfaces, and a second step of providing a tubular vessel having an introduction port in one end and a discharge port in the other end, and introducing the discharge fluid from the introduction port and growing the formed seed microparticle in the process of growth in the discharge fluid in the tubular vessel whereby obtaining a prescribed microparticle, wherein the first step and the second step are carried out continuously. a first step of forming a seed microparticle in a thin film fluid formed between at least two processing surfaces, a first processing surface and a second processing surface, which are disposed in a position they are faced with each other so as to be able to approach each other by using a surface-approaching pressure applying mechanism to apply a surface-approaching pressure, and to separate from each other by a separating force caused by viscosity and the pressure of the fluid, and maintaining the distance between the at least two processing surfaces at a predetermined minute distance by the balance between the surface-approaching pressure and the separating force, and where at least one of the processing surfaces rotates relative to the other, wherein in the first processing surface a groove-like depression extends in a radial direction and between the front edge of the depression and the outer peripheral edge of the first processing surface is formed a flat surface not having the depression, wherein a first fluid of the thin film fluid is introduced into between the processing surfaces, and a second fluid of the thin film fluid is introduced into between the processing surfaces from a separate path that is independent of the flow path introducing the first fluid and the second processing surface has an opening leading to between the processing surfaces, the opening being arranged in the second processing surface at a position opposite to the flat surface of the first processing surface such that mixing of the thin film fluid and formation of the seed microparticle is effected under laminar flow, whereby discharging a fluid which contains the seed microparticle in the process of growth thus formed as a discharge fluid from between the processing surfaces, and wherein in the first processing surface a groove-like depression extends in a radial direction and between the front edge of the depression and the outer peripheral edge of the first processing surface is formed a flat surface not having the depression, wherein a first fluid of the thin film fluid is introduced into between the processing surfaces, and a second fluid of the thin film fluid is introduced into between the processing surfaces from a separate path that is independent of the flow path introducing the first fluid and the second processing surface has an opening leading to between the processing surfaces, the opening being arranged in the second processing surface at a position opposite to the flat surface of the first processing surface such that mixing of the thin film fluid and formation of the seed microparticle is effected under laminar flow, whereby discharging a fluid which contains the seed microparticle in the process of growth thus formed as a discharge fluid from between the processing surfaces, and a second step of providing a tubular vessel having an introduction port in one end and a discharge port in the other end, and introducing the discharge fluid from the introduction port and growing the formed seed microparticle in the process of growth in the discharge fluid in the tubular vessel whereby obtaining a prescribed microparticle, wherein the first step and the second step are carried out continuously.