To provide an optical module excellent in airtightness of a protective member, in which a bonding state between a base portion and a cap is good, so that occurrence of leakage is minimized.SOLUTION: An optical module 1 of the present application includes a body portion 20 and a protective member. The protective member includes a base portion 10 and a cap 40. The cap 40 includes an upper wall portion 38, a side wall portion 39, and a flange portion 43 welded to a support surface 10A of the base portion 10. The flange portion 43 includes a curved portion 102 connected to the side wall portion 39 on a side opposite to a side connected to the upper wall portion 38, and a flat portion 100 connected to the curved portion 102 and projecting from the curved portion 102 toward the outside of the side wall portion 39. A ratio Wp/Wf of a flat width Wp of the flat portion 100 with respect to a flange width Wf that is a distance from an outer surface of the side wall portion 39 to an outer periphery 49 of the flange portion 43 in a planar shape viewed from an upper wall portion 38 side is 0.50 or more and 0.90 or less.SELECTED DRAWING: Figure 1
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