Particle separation device and method of separating particles

A particle separation device comprising at least:

• a separation flow path (i) to which a separation fluid containing a particle group including two types of particles being different in density is supplied, and (ii) through which the separation fluid flows in a certain direction;
• a divergence section connected to at least an end of the separation flow path in the certain direction in which the separation fluid flows,
• a first flow path formed from the divergence section in a rising direction;
• a second flow path formed from the divergence section in a falling direction;
• a first pool for collecting the separation fluid containing the particle group which flows through the first flow path;
• and
• a second pool for collecting the separation fluid containing the particle group which flows through the second flow path,
• wherein the separation flow path is formed in a horizontal direction, and
• wherein the divergence section has a plane double-layer Y structure wherein the first flow path and the second flow path are:
• (i) provided in two layers, respectively;
• (ii) branched to form a Y shape;
• and (iii) parallel to a maximum surface of a chip included in the particle separation device.