Provided is a microfluidic device including a lower panel including flow velocity measuring structures for measuring a flow velocity of a fluid; an upper panel separated from the lower panel and including a microfluidic channel through which a sample passes; a thin film provided at a portion where the lower panel and the upper panel adjoin each other in order to prevent the sample passing through the microfluidic channel from coming into direct contact with the flow velocity measuring structures, the thin film being configured to separate the lower panel and the upper panel to enable the lower panel to be repeatedly used multiple times; a specific functional unit configured to perform a specific operation on the sample passing through the microfluidic channel; and a negative pressure forming means configured to suck the lower panel and the upper panel with a negative pressure.