A small-sized fluid heating/cooling apparatus for heating or cooling a large amount of gas or liquid at a low cost. Structures where a flow passage for a fluid is formed in a heated or cooled base formed in a plate shape or a column shape, and a fluid which has passed through the narrowed flow passage impinges on a wall of a side face of the base vertically to perform heat exchange are connected in series. Heat exchange is instantaneously performed in a small space and manufacture of a mechanism performing such an operation is easy. A material constituting the flow passage may be a metal or ceramics, and a small-sized fluid heat exchanging apparatus can be manufactured at a low cost.