A plate stacking type heat exchanger 300 comprising: end plates 51 and 52; a plurality of pairs of core plates 53 and 54 stacked therebetween; and high temperature fluid compartments 55 through which high temperature fluid flows and low temperature fluid compartments 60 through which low temperature fluid flows defined in the space surrounded by the end plates 51 and 52 and the core plates 53 and 54 by bonding peripheral flanges of each of the pairs of core plates 53 and 54 to each other in a brazing process, the high and low temperature fluid compartments communicating with respective pairs of circulation holes 56a, 56b and 57a, 57b provided in one of the end plates 51 or 52, wherein each core of the core plates 53 and 54 is provided by forming a substantially flat plate and has a pair of an inlet port for high temperature fluid 58a and an outlet port for high temperature fluid 58b, which communicate with one of the pairs of circulation holes 56a and 56b, on one end side in the longitudinal direction of the plate and a pair of an inlet port for low temperature fluid 59a and an outlet port for low temperature fluid 59b, which communicate with the other pair of circulation holes 57a and 57b, on the other end side in the longitudinal direction of the plate, protrusions 53a and 54a are formed on one side of the plates, the protrusions extending from the inlet port for high temperature fluid 58a toward the other end side in the longitudinal direction of the plate, forming U-turn regions on the other end side in the longitudinal direction of the plate, and returning to the outlet port for high temperature fluid 58b, each of the pairs of core plates 53 and 54 is assembled to form the corresponding high temperature fluid compartment 55 in such a way that the side of one of the two core plates 53 and 54 that is opposite the one side faces the side of the other one of the two core plates that is opposite the one side and the protrusions 53a and 54a formed on the respective core plates 53 and 54 are paired but oriented in opposite directions, the low temperature fluid compartments 60 are formed between the pairs of core plates 53 and 54 and between the end 51 and 52 plates and the core plates 53 and 54 adjacent thereto, and a partition part is formed in each of the low temperature fluid compartments 60, the partition part partitioning along the longitudinal direction of the corresponding plates, the area where the U-turn regions are formed into an area including the inlet port for low temperature fluid 59a and an area including the outlet port for low temperature fluid 59b so as to form an inverse U-shaped flow path through which the low temperature fluid flows, the shape of which is an inverse shape of the U-turn regions for the high temperature fluid. end plates 51 and 52; a plurality of pairs of core plates 53 and 54 stacked therebetween; and high temperature fluid compartments 55 through which high temperature fluid flows and low temperature fluid compartments 60 through which low temperature fluid flows defined in the space surrounded by the end plates 51 and 52 and the core plates 53 and 54 by bonding peripheral flanges of each of the pairs of core plates 53 and 54 to each other in a brazing process, the high and low temperature fluid compartments communicating with respective pairs of circulation holes 56a, 56b and 57a, 57b provided in one of the end plates 51 or 52, wherein each core of the core plates 53 and 54 is provided by forming a substantially flat plate and has a pair of an inlet port for high temperature fluid 58a and an outlet port for high temperature fluid 58b, which communicate with one of the pairs of circulation holes 56a and 56b, on one end side in the longitudinal direction of the plate and a pair of an inlet port for low temperature fluid 59a and an outlet port for low temperature fluid 59b, which communicate with the other pair of circulation holes 57a and 57b, on the other end side in the longitudinal direction of the plate, protrusions 53a and 54a are formed on one side of the plates, the protrusions extending from the inlet port for high temperature fluid 58a toward the other end side in the longitudinal direction of the plate, forming U-turn regions on the other end side in the longitudinal direction of the plate, and returning to the outlet port for high temperature fluid 58b, each of the pairs of core plates 53 and 54 is assembled to form the corresponding high temperature fluid compartment 55 in such a way that the side of one of the two core plates 53 and 54 that is opposite the one side faces the side of the other one of the two core plates that is opposite the one side and the protrusions 53a and 54a formed on the respective core plates 53 and 54 are paired but oriented in opposite directions, the low temperature fluid compartments 60 are formed between the pairs of core plates 53 and 54 and between the end 51 and 52 plates and the core plates 53 and 54 adjacent thereto, and a partition part is formed in each of the low temperature fluid compartments 60, the partition part partitioning along the longitudinal direction of the corresponding plates, the area where the U-turn regions are formed into an area including the inlet port for low temperature fluid 59a and an area including the outlet port for low temperature fluid 59b so as to form an inverse U-shaped flow path through which the low temperature fluid flows, the shape of which is an inverse shape of the U-turn regions for the high temperature fluid.