A bulkhead heat exchanger comprising: a first bulkhead; a second bulkhead; and a plurality of flow path walls (48-1 to 48-n) which divide a space formed between the first bulkhead and the second bulkhead into a plurality of first flow paths, wherein the first bulkhead and the second bulkhead (61 separate the plurality of first flow paths from a second flow path through which a second fluid different from a first fluid flowing through the plurality of first flow paths flows, a plurality of wall surfaces (41, 42) are formed on the plurality of flow path walls (48-1 to 48-n), each of the plurality of wall surfaces (41, 42) conforms to a sine curve at different positions, and two adjacent flow path walls among a plurality of sinusoidal flow path walls arranged in an amplitude direction of the sine curve are sinusoidal flow path walls having a phase range of θ0 (= 0°) < θ1 < θ2 < 90° < θ3 < θ4 < 180° < θ5 < θ6 < 270° < θ7 < θ8 < θ0 (= 360°) as one period when a phase overlapping an inflection point of a sine curve of one flow path wall is θ0 (= 0°), characterized in that in the one flow path wall (122-1 to 122-n2), a main flow path wall element (124-1 to 124-m2) is formed in a portion overlapping a range of a phase θ of θ1 ≤ θ < θ3 and θ6 ≤ θ < θ8 by forming a portion (75, 90) which does not have the flow path wall in a portion overlapping a range of a phase θ of θ0 ≤ θ < θ1, θ3 ≤ θ < θ6 and θ8 ≤ θ < θ0, and in the other flow path wall (121-1 to 121-n1), a main flow path wall element (123-1 to 123-m1) is formed in a portion overlapping a range of a phase θ of θ2 ≤ θ < θ4 and θ5 ≤ θ < θ7 by forming a portion (73, 89) which does not have the flow path wall in a portion overlapping a range of a phase θ of θ0 ≤ θ < θ2, θ4 ≤ θ < θ5 and θ7 ≤ θ < θ0. a first bulkhead; a second bulkhead; and a plurality of flow path walls (48-1 to 48-n) which divide a space formed between the first bulkhead and the second bulkhead into a plurality of first flow paths, wherein the first bulkhead and the second bulkhead (61 separate the plurality of first flow paths from a second flow path through which a second fluid different from a first fluid flowing through the plurality of first flow paths flows, a plurality of wall surfaces (41, 42) are formed on the plurality of flow path walls (48-1 to 48-n), each of the plurality of wall surfaces (41, 42) conforms to a sine curve at different positions, and two adjacent flow path walls among a plurality of sinusoidal flow path walls arranged in an amplitude direction of the sine curve are sinusoidal flow path walls having a phase range of θ0 (= 0°) < θ1 < θ2 < 90° < θ3 < θ4 < 180° < θ5 < θ6 < 270° < θ7 < θ8 < θ0 (= 360°) as one period when a phase overlapping an inflection point of a sine curve of one flow path wall is θ0 (= 0°), characterized in that in the one flow path wall (122-1 to 122-n2), a main flow path wall element (124-1 to 124-m2) is formed in a portion overlapping a range of a phase θ of θ1 ≤ θ < θ3 and θ6 ≤ θ < θ8 by forming a portion (75, 90) which does not have the flow path wall in a portion overlapping a range of a phase θ of θ0 ≤ θ < θ1, θ3 ≤ θ < θ6 and θ8 ≤ θ < θ0, and in the other flow path wall (121-1 to 121-n1), a main flow path wall element (123-1 to 123-m1) is formed in a portion overlapping a range of a phase θ of θ2 ≤ θ < θ4 and θ5 ≤ θ < θ7 by forming a portion (73, 89) which does not have the flow path wall in a portion overlapping a range of a phase θ of θ0 ≤ θ < θ2, θ4 ≤ θ < θ5 and θ7 ≤ θ < θ0.