A multi-channel body having excellent heat exchanging effectiveness, gas separating effectiveness and high thermal shock resistance is characterized in that a large number of channels are formed independently by being surrounded with partition walls, said partition walls are connected with partition walls surrounding other independent channels, continuous channels are formed with the partition walls, outer wall and the connecting walls around each channel, and a part of said continuous passages open outward the outer wall and a side face of said continuous passage is integrally and air-tightly sealed with the outer wall at at least one end face where the channels open.