An object of the present invention is to provide a fluid control device with an improved effect of suppressing blowhole generation. Therefore, a component for a flow rate control device of the present invention includes: a first component 140 (A); a second component 107 (B) fixed to the first component by a press-fitting portion 802; a butt-welded portion 803 connecting the first component and the second component; and a first gap 1001 and a second gap 1002 formed between mutually opposing surfaces of the first component and the second component. The first gap is provided on a side of the press-fitting portion with respect to the second gap between the press-fitting portion and the butt-welded portion, and is formed in a direction intersecting a press-fitting direction. The second gap is provided on a side of the butt-welded portion with respect to the first gap between the press-fitting portion and the welded portion, and is formed in a direction intersecting the first gap.