In a heater core that constitutes part of a vehicular air conditioning apparatus, a plurality of first and second tubes are provided through which heated water flows through the interior thereof, and fins having louvers therein are disposed between the first and second tubes. Further, the heater core is equipped with a first heating section, which faces toward a first front passage through which air from a first blower unit flows, and a second heating section, which faces toward a first rear passage through which air from a second blower unit flows. Between the first heating section and the second heating section, a partitioning fin is disposed for blocking communication of air mutually between the first and second heating sections. Additionally, the first and second tubes are arranged in parallel to the direction in which the partitioning fin extends.