A transmitting device includes a partial data selector to select partial data divided from data to be transmitted over each of access networks based on a data transmission rate of each of the access networks; an identification information insertion unit to respectively insert identification information for measuring a data reception time interval into two or more partial data among the partial data selected for a particular access network of the access networks; a communication unit to transmit the two or more partial data with the inserted identification information to a receiving device through the particular access network; and a controller to acquire transmission state information of the particular access network based on at least one of a data transmission time interval and a data reception time interval.