A physical quantity detector includes a housing, a circuit board, a cover, a resin member, a conductor, and a conductive member. The circuit board includes a board surface. The cover faces the board surface and defines, together with the hosing, a passage through which the target fluid flows. The conductor includes a passage side portion and a connecting portion. The conductive member electrically connects the connecting portion to the circuit board. The conductive member includes a first end in the thickness direction facing a contact target that is either one of the connecting portion or the board surface. The first end includes a contact portion in contact with the contact target and a contactless portion away from the contact target in the thickness direction.