A liquid surface sensing device includes a rotational body that is made of resin and rotates according to upward and downward motion of a surface of liquid in a container, a magnet that is held by the rotational body to rotate together with the rotational body, a stationary body that is fixed to the container and rotatably bears the rotational body, and a magnetoelectric conversion element that is embedded in the stationary body and detects a magnetic field generated by the magnet to output an electric signal indicating the liquid surface. The rotational body includes a storage space that accommodates the magnet, a resilient claw that projects into the storage space and is in contact with the magnet in its resiliently deformed state to press the magnet on a storage wall for the storage space, and a projection that projects from an opposite side of the magnet toward the resilient claw in the storage space and expands to be in contact with the resilient claw.