A micro-fluidic chip extending in a length direction, a width direction, and a height direction, the three directions being orthogonal to each other, comprising: a flow channel having a communicating port at its downstream end in the length direction, a cavity communicating with the communicating port of the flow channel; a microtube formed of a voltage-applicable metal and configured to introduce a first liquid into a laminar flow of a second liquid passing through the flow channel, wherein the microtube and the flow channel are adapted to send the first liquid and the second liquid to the communicating port of the flow channel in such a way that a laminar flow of the first liquid introduced from the microtube is surrounded by the laminar flow of the second liquid: a piezoelectric element arranged upstream of the communicating port, wherein the piezoelectric element is configured to turn the liquid flow to the droplet and the shape of the communicating port is configured to promote the turning of the liquid flow to the droplet, such that the charged droplet is formed to contain the first and second liquids and to be introduced into the cavity through the communicating port; at least two branch areas communicating with the cavity at its downstream end in the length direction, the cavity being increased in width direction from the communicating port to the branch areas and having a height in the height direction of 300μm to 5mm, being 10 to 100 times the size of the droplets to be introduced Into the cavity; and at least two electrodes (41, 42) provided on both sides along the cavity and configured to control a movement direction of a droplet in the width direction within the cavity from the communication port to an arbitrarily selected branch area based on electric force acting between the charged droplet and the electrodes (41, 42). a flow channel having a communicating port at its downstream end in the length direction, a cavity communicating with the communicating port of the flow channel; a microtube formed of a voltage-applicable metal and configured to introduce a first liquid into a laminar flow of a second liquid passing through the flow channel, wherein the microtube and the flow channel are adapted to send the first liquid and the second liquid to the communicating port of the flow channel in such a way that a laminar flow of the first liquid introduced from the microtube is surrounded by the laminar flow of the second liquid: a piezoelectric element arranged upstream of the communicating port, wherein the piezoelectric element is configured to turn the liquid flow to the droplet and the shape of the communicating port is configured to promote the turning of the liquid flow to the droplet, such that the charged droplet is formed to contain the first and second liquids and to be introduced into the cavity through the communicating port; at least two branch areas communicating with the cavity at its downstream end in the length direction, the cavity being increased in width direction from the communicating port to the branch areas and having a height in the height direction of 300μm to 5mm, being 10 to 100 times the size of the droplets to be introduced Into the cavity; and at least two electrodes (41, 42) provided on both sides along the cavity and configured to control a movement direction of a droplet in the width direction within the cavity from the communication port to an arbitrarily selected branch area based on electric force acting between the charged droplet and the electrodes (41, 42). a piezoelectric element arranged upstream of the communicating port, wherein the piezoelectric element is configured to turn the liquid flow to the droplet and the shape of the communicating port is configured to promote the turning of the liquid flow to the droplet, such that the charged droplet is formed to contain the first and second liquids and to be introduced into the cavity through the communicating port; at least two branch areas communicating with the cavity at its downstream end in the length direction, the cavity being increased in width direction from the communicating port to the branch areas and having a height in the height direction of 300μm to 5mm, being 10 to 100 times the size of the droplets to be introduced Into the cavity; and at least two electrodes (41, 42) provided on both sides along the cavity and configured to control a movement direction of a droplet in the width direction within the cavity from the communication port to an arbitrarily selected branch area based on electric force acting between the charged droplet and the electrodes (41, 42).