A microchip comprising therein a first channel which allows inflow of a first liquid selected from whole blood, platelet-rich plasma and a drug-treated liquid thereof, a second channel connected to the first channel, which allows inflow of a second liquid containing an agent that is reactive with the first liquid, and a merged channel extended from the connection portion of the first channel with the second channel, wherein, in the merged channel, a stirring section having a stirring bar for mixing the first liquid with the second liquid is provided; and a blood monitoring device using the same.