Abstract: Apparatus for producing fine particles having a particle formation mechanism and a particle-outlet micro-channel may include a unit-structure including first and second portions adjacent to each other; and a first inlet defined in the first portion at a first height. A continuous phase solution is injected into the first inlet; and a second inlet is defined in the first portion at a second height different from the second height. A dispersed phase solution is injected into the second inlet. A merging volume is defined in the second portion and is defined at third height equal to either the first height and the second height, or has a value therebetween. The continuous phase solution and the dispersed phase solution are merged in the merging volume, wherein fine particles are formed. A first micro-channel and a second micro-channel branching from the merging volume communicates with the first inlet and the second inlet, respectively.