A toilet apparatus comprising: a main part including a function part, and a case cover covering the function part, the main part being attached on a toilet bowl; and a toilet seat attached rotatably to the case cover, the toilet seat shifting between a closed state and an open state, in the closed state a user being capable of seating upward the toilet bowl, in the open state an upper surface of the toilet bowl being exposed, the case cover including an extending portion, a height of the extending portion becoming low toward forward, the toilet seat including a toilet seat main body including a first portion and a second portion, the first portion being positioned forward the case cover in the closed state, the second portion rising backward from the first portion in the closed state, overlapping the extending portion, and being pivotally supported to the case cover, and a heating part incorporated in the toilet seat main body, and heating a seating surface of the toilet seat main body, wherein the extending portion having an upper end surface changing to lower a height toward forward, wherein said upper end surface of the extending portion has a convex curved surface shape in a manner to change to lower a height toward sides, and a lower end surface of the second portion of the toilet seat main body has a concave curved surface shape in a manner to change along the upper end surface of the extending portion to lower a height toward the sides in the closed state wherein a curvature of the lower end surface of the second portion at a prescribed position is generally same as a curvature of the upper end surface of the extending portion at a position opposing the prescribed position in the closed state so that the lower end surface of the second portion is generally parallel to the upper end surface of the extending portion in a cross-section orthogonal to the front-back direction. a main part including a function part, and a case cover covering the function part, the main part being attached on a toilet bowl; and a toilet seat attached rotatably to the case cover, the toilet seat shifting between a closed state and an open state, in the closed state a user being capable of seating upward the toilet bowl, in the open state an upper surface of the toilet bowl being exposed, the case cover including an extending portion, a height of the extending portion becoming low toward forward, the toilet seat including a toilet seat main body including a first portion and a second portion, the first portion being positioned forward the case cover in the closed state, the second portion rising backward from the first portion in the closed state, overlapping the extending portion, and being pivotally supported to the case cover, and a heating part incorporated in the toilet seat main body, and heating a seating surface of the toilet seat main body, wherein the extending portion having an upper end surface changing to lower a height toward forward, wherein said upper end surface of the extending portion has a convex curved surface shape in a manner to change to lower a height toward sides, and a lower end surface of the second portion of the toilet seat main body has a concave curved surface shape in a manner to change along the upper end surface of the extending portion to lower a height toward the sides in the closed state wherein a curvature of the lower end surface of the second portion at a prescribed position is generally same as a curvature of the upper end surface of the extending portion at a position opposing the prescribed position in the closed state so that the lower end surface of the second portion is generally parallel to the upper end surface of the extending portion in a cross-section orthogonal to the front-back direction.