A microchip is provided that includes a flow path through which a liquid containing a micro particle flows, an orifice through which the liquid flowing through the flow path is discharged into a space outside the microchip, and a light-irradiated portion provided at a predetermined location of the flow path and configured to be irradiated with light. A width of the flow path and a depth of the flow path at the orifice are set to be smaller than a width of the flow path and a depth of the flow path at the light-irradiated portion, and the flow path is configured to gradually decrease from upstream of the orifice in a cross-section area perpendicular to a liquid-delivering direction between the light-irradiated portion and the orifice. A cartridge including the microchip is also provided.