The invention relates to a high-compactness heat exchanger, in particular to a multi-stream printed circuit board type heat exchanger. The heat exchanger comprises at least one group of a cold fluid inlet and a cold fluid outlet, at least one group of a hot fluid inlet and a hot fluid outlet, and a heat exchanging core. The sum of the number of the group of the cold fluid inlet and the cold fluidoutlet, and the number of the groups of the hot fluid inlets and the hot fluid outlets is at least three. The heat exchanging core comprises a plurality of cold fluid channel plates and a plurality ofhot fluid channel plates and is formed by piling and connecting the cold fluid channel plates and the hot fluid channel plates by means of a diffusion bonding technology. According to the multi-stream printed circuit board type heat exchanger, the structure is compact, heat exchanging between multiple streams of cold and hot fluids is achieved, the heat exchanger has the characteristics of high heat exchanging efficiency, convenient mounting and energy saving, and the technical defects that an existing heat exchanger is prone to leaking and low in pressure-bearing capacity can be effectivelyovercome.