Heat exchanger and vehicle air conditioning device

A heat exchanger comprising:

• a plurality of heat exchange cores through which a first heat medium flows;
• and
• a case of which an inside is divided into a plurality of chambers by a partition portion,
• wherein the heat exchange cores are each accommodated in the chambers adjacent to each other through the partition portion,
• each of the chambers is configured such that a second heat medium flows therethrough and heat is exchanged between the second heat medium and the first heat medium,
• each of the chambers has an inlet and an outlet for the second heat medium, and is configured to cause the second heat medium to circulate in the each of the chambers to exchange heat between the second heat medium and the first heat medium, and
• a channel for the second heat medium on a downstream side in each of the chambers is provided at a position farther from the partition portion than a channel for the second heat medium on an upstream side.