Heat exchanging member and heat exchanger

A heat exchanging member includes: a pillar shape honeycomb structure having an outer peripheral wall and partition walls extending through the honeycomb structure from a first end face to a second end face to define a plurality of cells forming a through channel of a first fluid, and a covering member for covering the outer peripheral wall of the honeycomb structure. In a cross section of the honeycomb structure perpendicular to a flow direction of the first fluid, the partition walls includes: a plurality of first partition walls extending in a radial direction from the side of a center portion of the cross section; and a plurality of second partition walls extending in a circumferential direction, and a number of the first partition walls on the side of the central portion is less than a number of the first partition walls on the side of the outer peripheral wall.