Provided are a heat exchanger having a novel structure and efficiently cooling a heat generating body, and a method of manufacturing the heat exchanger. A heat exchanger has flow paths formed by being closed by an upper plate and a lower plate which have rectilinearly formed upstanding fins parallelly arranged at specific intervals, and gaps extend between adjacent fins in the top-bottom direction along the direction in which the fins extend. Either of or both the upper plate and the lower plate are provided with projections arranged in the longitudinal direction of the flow path and projecting inward of the flow path.