To provide a method for electron beam welding of aluminum or an aluminum alloy material which does not create weld defects, which is excellent in safety and which yields high joint strength.

A first member 1 and a second member 2 made of an aluminum plate or an aluminum alloy plate are prepared, and an L-shaped notch 5 is provided on the end face of the first member 1. On the base corner of the notch 5, a groove 3 is formed. After erecting the first member 1 vertically with the end face on which the notch 5 is formed directed upward, and after making the tip part of the second member 2 horizontal, the second member 2 is fitted to the notch 5 of the first member 1, thereby forming a square joint. Subsequently, both members are welded by irradiating a joint formed between the first member 1 and the second member 2 with an electron beam 4 from the end face side of the first member 1. At this time, when the thickness of a part on which the notch 5 of the first member 1 is provided is t mm, the width of the base of the notch 5 is f mm, the width of the groove 3 is g mm and the depth of the groove 3 is h mm, g must be ≤0.4f and h must be ≤0.5t.