Provided are a centrifugal force based microfluidic device which can automatically perform a dilution operation and a microfluidic system including the same. The centrifugal force based microfluidic device for dilution includes a rotatable disk type platform, a mixing chamber disposed on the platform; a buffer solution storage disposed on a portion of the platform which is closer to a center of the platform than the mixing chamber, connected to the mixing chamber through a channel to supply a predetermined amount of buffer solution to the mixing chamber at least one time, and a plurality of diluted solution chambers which are disposed on a portion of the platform which is farther from the center of the platform than the mixing chamber, are each connected to the mixing chamber through flow paths extended from a middle exit corresponding to a predetermined water level, and sequentially receiving a solution which is serially diluted in the mixing chamber at least one time.