A liquid-level detection device detects a level of a surface of liquid stored in a container. The liquid-level detection device includes: a float that floats on the surface of liquid; a rotatable body that rotates due to a upward or downward displacement of the float and includes a rotation contact part; a supporting body that rotatably supports the rotatable body and includes a supporting contact part which is located on a rotational track of the rotation contact part to restrict the rotation of the rotatable body in a specified direction by contact between the supporting contact part and the rotation contact part; and an attachment member that is attached to the supporting body and includes an attachment contact part which makes contact with the rotatable body rotating in the specified direction to prevent the contact of the rotation contact part with the supporting contact part.