A heat transport device comprises first flow passages through which a first fluid flows, and second flow passages through which a second fluid flows, wherein a cross-section A satisfying the following Requirement 1 to Requirement 3 can be achieved. Requirement 1 is that the cross-section A is a cross-section perpendicular to the second flow passages. Requirement 2 is that the holes of the second flow passages are disposed so as to be aligned in the left-right direction and to form layers in the up-down direction; and when comparing layers with holes adjacent in the up-down direction, the holes of the second flow passages are not disposed at the same position in the left-right direction. Requirement 3 is that the first flow passages exist between the layers with holes adjacent in the up-down direction, and the first flow passages meander in the up-down direction so as to avoid the holes of the second flow passages in the layers with holes that are sandwiched in the up-down direction.