A capacitance detection device includes a first electrode (1) and a second electrode (2) at least partially facing each other with a conveyance path (5) therebetween, the conveyance path extending along a conveyance direction in which a sheet-like detection object (3) is conveyed, an oscillating circuit to form an electric field (9) between the first electrode (1) and the second electrode (2), a detection circuit to detect a change in capacitance between the first electrode (1) and the second electrode (2), a first board (11) and a second board (12) including at least one of the oscillating circuit or the detection circuit, an insulative first plate (6) arranged between the first electrode (1) and the conveyance path (5), and an insulative second plate (7) arranged between the second electrode (2) and the conveyance path (5).