A children's toilet apparatus is disclosed that is convertible from a free-standing potty chair to a toilet trainer that cooperates with a conventional toilet. The apparatus principally comprises a toilet seat member and adjustable legs which are pivotally interconnected. When employed as a free-standing potty chair, the leg members independently support the toilet seat member. When utilized as a toilet trainer, the leg members are oriented so that the toilet seat member is stabilized on and about the water closet seat of a conventional toilet by virtue of the interconnection of the toilet seat member and the leg members and contact of one of the leg members with a floor surface. In a preferred arrangement, one of the leg members is provided with a step member and hand grips to aid children in positioning themselves on top of the toilet seat member when the apparatus is employed as a toilet trainer.