In a micro chemical apparatus, guide walls as physical barriers are provided at a region where fluid A and fluid B as unmixed raw materials and a product are discharged so that, when the fluid A and the fluid B as raw materials are charged, only the portion in which the fluid A and the fluid B are mixed and allowed to react with each other by molecular diffusion of the raw materials is discharged. As a result, only the product is in the range between the two guide walls, and the product can be selectively taken out of the outlet.