The present invention provides a monopole tower having a tower supporting structure in which the outer dimension of a tower shell is the maximum dimension by eliminating a base plate which extends toward the outside of the tower shell. In a monopole tower provided upright on a foundation B, a lower end side of the tower 2 comprised a tower-side coupling member in a range equal to or less than outside diameter of a tower shell 21. In a space comprising a foundation-side coupling member provided on the foundation B, the foundation-side coupling member and the tower-side coupling member are coupled by welding, a bolt using a splice plate, or a rivet.