Provided is a microchip capable of integrating liquid evaporation as an operation on the microchip. In the microchip 10 having a gas flow path 13 inside, liquid is dispersed by capillary action and pooled in a pool portion 12 at a bottom of the gas flow path 13, and at least a part of the liquid pooled in the pool portion 12 is evaporated. As the capillary action is used, the liquid can be dispersed and pooled in the pool portion 12 at the bottom of the gas flow path 13 inside the microchip 10. Besides, the liquid pooled in the pool portion 12 remains in the pool portion by a surface tension even if gas is made to flow in the gas flow path 13 or the gas flow path is evacuated for evaporation. This enables highly efficient evaporation inside the microchip 10.