A main girder for a crane, wherein the main girder comprises a splice joint, whereby the main girder comprises at least two longitudinal main girder parts to be connected to each other by their ends and each having a central web which comprises at least one web plate, a longitudinal upper flange or top plate arranged to the top part of the central web as well as a longitudinal lower flange which is arranged to the bottom part of the central web and which protrudes from the central web to its both sides, the main girder is suited to be supported by the ends as supporting main girder without intermediate supports between the ends, a splice joint configured to connect the at least two longitudinal main girder parts, characterised in that the splice joint comprises - on both outer sides of the central web, a plate-like tongue-and-groove joint receiving the shear forces of the splice joint, the tongue-and-groove joint in each case comprising a tongue fixed to the central web of a first main girder part of the at least two longitudinal main girder parts to be joined, and a groove fixed to the central web of a second main girder part of the at least two longitudinal main girder parts to be joined; and - a lower flange joint (9; 90) receiving the bending forces of the splice joint, - whereby the tongue-and-groove joints on opposite outer sides of the web are arranged reversed in relation to each other, and whereby the tongues and grooves (7, 8) are located on opposite sides of the web in reverse relation to each other, and - whereby the shaping of the tongues and grooves (7, 8) allowing fitting beside each other in the axial direction, in other words, the male and female surfaces, as to their longitudinal sides, of the tongues and grooves (7, 8) placed in a butt joint are so formed that the axial setting is possible by a linear motion. a splice joint configured to connect the at least two longitudinal main girder parts, characterised in that the splice joint comprises - on both outer sides of the central web, a plate-like tongue-and-groove joint receiving the shear forces of the splice joint, the tongue-and-groove joint in each case comprising a tongue fixed to the central web of a first main girder part of the at least two longitudinal main girder parts to be joined, and a groove fixed to the central web of a second main girder part of the at least two longitudinal main girder parts to be joined; and - a lower flange joint (9; 90) receiving the bending forces of the splice joint, - whereby the tongue-and-groove joints on opposite outer sides of the web are arranged reversed in relation to each other, and whereby the tongues and grooves (7, 8) are located on opposite sides of the web in reverse relation to each other, and - whereby the shaping of the tongues and grooves (7, 8) allowing fitting beside each other in the axial direction, in other words, the male and female surfaces, as to their longitudinal sides, of the tongues and grooves (7, 8) placed in a butt joint are so formed that the axial setting is possible by a linear motion. - on both outer sides of the central web, a plate-like tongue-and-groove joint receiving the shear forces of the splice joint, the tongue-and-groove joint in each case comprising a tongue fixed to the central web of a first main girder part of the at least two longitudinal main girder parts to be joined, and a groove fixed to the central web of a second main girder part of the at least two longitudinal main girder parts to be joined; and - a lower flange joint (9; 90) receiving the bending forces of the splice joint, - whereby the tongue-and-groove joints on opposite outer sides of the web are arranged reversed in relation to each other, and whereby the tongues and grooves (7, 8) are located on opposite sides of the web in reverse relation to each other, and - whereby the shaping of the tongues and grooves (7, 8) allowing fitting beside each other in the axial direction, in other words, the male and female surfaces, as to their longitudinal sides, of the tongues and grooves (7, 8) placed in a butt joint are so formed that the axial setting is possible by a linear motion.