A railcar truck configured to support a carbody via secondary springs, the railcar truck comprising a pair of side beams having concavities configured to receive the secondary springs, each of the side beams includes: a side beam outer wall located on an outer side in a railcar width direction and extending in a railcar-longitudinal direction; a side beam inner wall located on an inner side with respect to the side beam outer wall in the railcar width direction and extending in the railcar-longitudinal direction; a side beam lower wall extending in the railcar-longitudinal direction and on which the secondary spring is placed; and a side beam upper wall having an opening through which an upper portion of the received secondary spring projects, the side beam upper wall extending in the railcar-longitudinal direction, each of the concavities being formed by the side beam outer wall, the side beam inner wall and the side beam lower wall, and receiving the secondary spring through the opening, and in each of the side beams, a cross-sectional area of an opening-existing portion where the opening is formed being greater than a cross-sectional area of an opening-non-existing portion where the opening is not formed, characterised in that in the opening-existing portion, the railcar truck further comprises: a first reinforcing member located between the side beam outer wall and the opening, and extending from the side beam lower wall in a vertical direction; and a second reinforcing member located between the side beam inner wall and the opening, and extending from the side beam lower wall in the vertical direction, the railcar truck further comprising: a rectangular first closed cross-section formed by the side beam outer wall, the side beam upper wall, the first reinforcing member, and the side beam lower wall; and a rectangular second closed cross-section formed by the side beam inner wall, the side beam upper wall, the second reinforcing member, and the side beam lower wall. a side beam outer wall located on an outer side in a railcar width direction and extending in a railcar-longitudinal direction; a side beam inner wall located on an inner side with respect to the side beam outer wall in the railcar width direction and extending in the railcar-longitudinal direction; a side beam lower wall extending in the railcar-longitudinal direction and on which the secondary spring is placed; and a side beam upper wall having an opening through which an upper portion of the received secondary spring projects, the side beam upper wall extending in the railcar-longitudinal direction, each of the concavities being formed by the side beam outer wall, the side beam inner wall and the side beam lower wall, and receiving the secondary spring through the opening, and in each of the side beams, a cross-sectional area of an opening-existing portion where the opening is formed being greater than a cross-sectional area of an opening-non-existing portion where the opening is not formed, characterised in that in the opening-existing portion, the railcar truck further comprises: a first reinforcing member located between the side beam outer wall and the opening, and extending from the side beam lower wall in a vertical direction; and a second reinforcing member located between the side beam inner wall and the opening, and extending from the side beam lower wall in the vertical direction, the railcar truck further comprising: a rectangular first closed cross-section formed by the side beam outer wall, the side beam upper wall, the first reinforcing member, and the side beam lower wall; and a rectangular second closed cross-section formed by the side beam inner wall, the side beam upper wall, the second reinforcing member, and the side beam lower wall. a first reinforcing member located between the side beam outer wall and the opening, and extending from the side beam lower wall in a vertical direction; and a second reinforcing member located between the side beam inner wall and the opening, and extending from the side beam lower wall in the vertical direction, the railcar truck further comprising: a rectangular first closed cross-section formed by the side beam outer wall, the side beam upper wall, the first reinforcing member, and the side beam lower wall; and a rectangular second closed cross-section formed by the side beam inner wall, the side beam upper wall, the second reinforcing member, and the side beam lower wall. a rectangular first closed cross-section formed by the side beam outer wall, the side beam upper wall, the first reinforcing member, and the side beam lower wall; and a rectangular second closed cross-section formed by the side beam inner wall, the side beam upper wall, the second reinforcing member, and the side beam lower wall.