A raindrop detection device includes a first fixing member which is fixed to a windshield and has a first engagement portion, an inner housing in which a detection unit is accommodated, an outer housing in which the inner housing is accommodated and which is fixed to the inner housing, a second fixing member having a second engagement portion which is detachably engaged with the first engagement portion of the first fixing member, and a leaf spring which is engaged with the inner housing to press and bias the inner housing toward the windshield. The second fixing member has a leaf-spring biasing portion, which contacts the leaf spring to elastically bias the leaf spring toward the windshield at a predetermined pressing force.