The present invention provides a miniaturized microfluidic device with a heater that has a simple structure without needing adhesion means for improving the heat transfer between the heater block and the device, and which can form the uniform temperature regions. Disclosed is a microfluidic device, including: a substrate; a reaction flow path formed on the substrate; and a temperature adjustment heater for heating the reaction flow path, in which a reaction flow path formation region including the reaction flow path formed therein and a temperature adjustment heater formation region including the temperature adjustment heater formed therein are alternately arranged on the substrate, the reaction flow path is formed to be bent at least one time in the reaction flow path formation region, and the temperature adjustment heater is formed to be bent at least one time in the temperature adjustment heater formation region.