A method for manufacturing an electron source comprising steps of: preparing a plurality of first members each provided with a columnar portion made of a first material having an electron emission characteristic and with an end face; preparing a plurality of second members (2,12) each made of a second material having a higher work function and a lower strength than the first material, wherein the second material is glassy carbon, and each of which comprising a tubular portion in which a hole (3,13) extending in a direction from one end face toward the other end face is formed; selecting one first member from the plurality of first members and selecting one second member (2,12) from the plurality of second members (2,12); and pressing the columnar portion of the selected first member into the hole (3,13) of the selected second member (2,12), wherein, in a cross-section orthogonal to a longitudinal direction of the columnar portion, each of the columnar portions of the plurality of first members has a substantially quadrangular cross-sectional shape, and each of the holes (3,13) of the plurality of second members (2,12) has a substantially circular cross-sectional shape, in the step, a set of the first member and the second member (2,12) satisfying the following condition is selected from the plurality of first members and the plurality of second members (2,12), <Condition> L 1 / R 1 > 1 in the inequality, L 1 indicates a length of the longer one of two diagonals of the substantially quadrangular shape, and R 1 indicates a diameter of the hole (3,13), and in the step, by pressing the columnar portion into the hole (3,13) of the second member (2,12), a portion of a side surface of the columnar portion abuts an inner surface of the tubular portion of the second member (2,12), thereby fixing the columnar portion to the second member (2,12); and wherein the end face of the columnar portion and the one end face of the second member (2,12) form a flat surface, and wherein the entire side-surface of the columnar portion is covered by the tubular portion. preparing a plurality of first members each provided with a columnar portion made of a first material having an electron emission characteristic and with an end face; preparing a plurality of second members (2,12) each made of a second material having a higher work function and a lower strength than the first material, wherein the second material is glassy carbon, and each of which comprising a tubular portion in which a hole (3,13) extending in a direction from one end face toward the other end face is formed; selecting one first member from the plurality of first members and selecting one second member (2,12) from the plurality of second members (2,12); and pressing the columnar portion of the selected first member into the hole (3,13) of the selected second member (2,12), wherein, in a cross-section orthogonal to a longitudinal direction of the columnar portion, each of the columnar portions of the plurality of first members has a substantially quadrangular cross-sectional shape, and each of the holes (3,13) of the plurality of second members (2,12) has a substantially circular cross-sectional shape, in the step, a set of the first member and the second member (2,12) satisfying the following condition is selected from the plurality of first members and the plurality of second members (2,12), <Condition> L 1 / R 1 > 1 in the inequality, L 1 indicates a length of the longer one of two diagonals of the substantially quadrangular shape, and R 1 indicates a diameter of the hole (3,13), and in the step, by pressing the columnar portion into the hole (3,13) of the second member (2,12), a portion of a side surface of the columnar portion abuts an inner surface of the tubular portion of the second member (2,12), thereby fixing the columnar portion to the second member (2,12); and wherein the end face of the columnar portion and the one end face of the second member (2,12) form a flat surface, and wherein the entire side-surface of the columnar portion is covered by the tubular portion.