To provide a micro sample inlet method for quantitatively introducing a trace amount of samples to channels in a microfluidic device, and to provide a microfluidic device provided with a micro chromatograph.

The microfluidic device comprises a fist flow inlet, a first flow exit, a first channel connecting both, a first branch part for dividing the first channel into two, a second channel branching from the first branch part, and a second flow inlet provided for the other end of the second channel. In the micro sample inlet method, a first process and a second process are executed. In the first process, a second pump, connected to the first flow inlet for discharging a fluid for transfer, is brought into a halt or operating state, and a first pump, connected to the first flow outlet, is operated in a suction direction at a speed higher than the discharge speed of the second pump to transfer the fluid for transfer in the first channel, in the direction of the first pump, and simultaneously transfers a sample in the second channel to a downstream part of the first channel by negative pressure generated by the difference in speeds between both pumps. In the second process, the inflow of the sample is halted, by making the difference in the speeds of both pumps to be zero or make it reversed, when a prescribed amount of the sample has been introduced.

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