NOVELTY - The unit (1) has a thermoelectric conversion element (2a) provided between a pair of substrates (2b, 2c). A frame is mounted along an outer peripheral portion of the pair of substrates. A case (3) is formed with a flow channel (3h) with an opened structure, where an opening portion of the channel is covered with one of the substrates. The case comprises a peripheral wall portion (3j) to cover the outer peripheral portion of the frame, where the peripheral wall portion of the case and the outer peripheral portion of the frame contact each other to achieve sealing.    USE - Thermoelectric conversion unit for use in a heat exchange system provided on a vehicle to cool or heat a cabin or a component i.e. battery, of the vehicle.    ADVANTAGE - The unit has simple structure, and the thermoelectric conversion elements can be securely held between the pair of substrates. The case formed with the flow channel can be mounted in a secure manner. The frame can hold the pair of the substrates, and the thermoelectric conversion elements via the pair of the substrates, and can be easily configured due to structure extending along the outer peripheral portions the pair of substrates, so that the case and the frame can tightly contact with each other and can be mounted with each other with high stability. The case can be formed with arcuate portions having shape corresponding to arcuate portions of the frame such that four corners of the frame are able to withstand concentrated forces applied to the corners, so that sealing property of the portion between the frame and the case can be improved.    DETAILED DESCRIPTION - The thermoelectric conversion element is a Peltier element providing Peltier effect, or an element providing Seebeck Effect or Thomson Effect.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of a thermoelectric conversion unit.    Thermoelectric conversion unit (1)    Thermoelectric conversion modules (2)    Thermoelectric conversion element (2a)    Pair of substrates (2b, 2c)    Fins (2d, 2e)    Case (3)    Top panel of case (3a)    Bottom panel of case (3b)    Side panels of case (3c, 3d)    Front panel of case (3e)    Flow channels (3h, 3i)    Peripheral wall portion (3j)