A method of joining wood structures (3a, 3b) to one another, the method comprising: selecting a joining element comprising: at least two joint holes for pin joints, a first plane surface and a second plane surface, the first plane surface and the second plane surface being arranged on opposite sides of the joining element in a mutually substantially parallel manner and arranged to define a middle area of the joining element, and an inclined surface (9a, 9b) slanting towards an outer edge of the joining element and arranged at an angle with respect to at least one said plane surface; providing a joining surface (4a, 4b) of each wood structure (3a, 3b) to be joined with a groove (5a, 5b) such that the joining element is arrangeable in a space formed by the grooves (5a, 5b) provided in the wood structures to be joined when the wood structures are placed against one another with the joining surfaces (4a, 4b) of the wood structures facing one another, and in that the space has substantially the same size and shape as the joining element; arranging a binding agent in the groove provided in at least one wood structure to be joined, arranging the joining element in the groove of at least one wood structure to be joined, and joining the wood structures to one another with the joining surfaces facing one another, such that the joining element and the binding agent substantially fill the space up; and arranging a joint pin in each joint hole of the joining element through at least one wood structure to be joined in order to lock the wood structures in place with respect to one another; wherein the joining element comprises a first curved part and a second curved part at mutually opposite ends (10a, 10b), and the method further comprises arranging the groove to be formed in each wood structure to be joined to comprise a shape substantially in conformity with that of the first or the second curved part (11a, 11b). at least two joint holes for pin joints, a first plane surface and a second plane surface, the first plane surface and the second plane surface being arranged on opposite sides of the joining element in a mutually substantially parallel manner and arranged to define a middle area of the joining element, and an inclined surface (9a, 9b) slanting towards an outer edge of the joining element and arranged at an angle with respect to at least one said plane surface; providing a joining surface (4a, 4b) of each wood structure (3a, 3b) to be joined with a groove (5a, 5b) such that the joining element is arrangeable in a space formed by the grooves (5a, 5b) provided in the wood structures to be joined when the wood structures are placed against one another with the joining surfaces (4a, 4b) of the wood structures facing one another, and in that the space has substantially the same size and shape as the joining element; arranging a binding agent in the groove provided in at least one wood structure to be joined, arranging the joining element in the groove of at least one wood structure to be joined, and joining the wood structures to one another with the joining surfaces facing one another, such that the joining element and the binding agent substantially fill the space up; and arranging a joint pin in each joint hole of the joining element through at least one wood structure to be joined in order to lock the wood structures in place with respect to one another; wherein the joining element comprises a first curved part and a second curved part at mutually opposite ends (10a, 10b), and the method further comprises arranging the groove to be formed in each wood structure to be joined to comprise a shape substantially in conformity with that of the first or the second curved part (11a, 11b).