A heater sheet is configured to be applied to a cover of a vehicle-mounted sensor. The heater sheet is provided with a sheet substrate which is attached to the cover, and at least one heat generating strip which is provided along the sheet substrate. The heat generating strip is formed in a mesh shape in which a large number of filamentous first electrical conductors and a large number of filamentous second electrical conductors intersect one another. The first electrical conductors and the second electrical conductors are arranged in such a way as to be inclined relative to a horizontal direction.