In the case of passing a reagent in a reaction channel in a microchip, which carries a reactant capable of reacting with the reagent on the wall thereof, and bringing the reactant into contact with the reagent so as to carry out a reaction, the reagent is efficiently passed to the reactant to thereby promote the progress of the reaction. In carrying out the reaction as described above, the reagent (30a) is passed in such a manner that the periphery of the gas/liquid interface at the front end of the reagent moves forward and backward along the wall face of the reaction channel (10). After the completion of the reaction between the reagent (30a) and the reactant, another reagent (30b), which is to be reacted with the reactant capable of reacting with the reagent that is carried on the reaction channel, is passed into the reaction channel (10) while providing a gas in the front edge side thereof. In carrying out the reaction, the reagent (30b) is passed in such manner that the periphery of the gas/liquid interface at the front end of the reagent moves forward and backward along the wall face of the reaction channel (10).