Multi-tube heat exchanger (1) including a bundle of tubes (6) which form fluid passages of first heat exchanging fluid, an outer shell (1a) which covers the bundle of tubes (6) and form a fluid passage of second heat exchanging fluid, and a baffle plate (7) which is arranged inside the outer shell (1a) in a direction intersecting an axial direction of the bundle of tubes (6) and provided with a plurality of through holes (8) through which respective tubes (6) of the bundle are passed. Each of the through holes (8) has such a shape that a portion of an outer peripheral face of the tube (6) comes into contact with a portion of an inner peripheral face of the through hole (8), and a gap for passing the second heat exchanging fluid is formed between the other portion of the inner peripheral face and the outer peripheral face of the tube (6).