A modular door case for bathing enclosure includes two jambs, two frame members, and four fasten components. Each frame member has an accommodating portion at ends thereof, and at least one pair clasp holes respectively formed on upper and lower walls of the accommodating portion. Each fasten component has a base, at least one pair of clasp members, and at least one compelling bolt. A clasp protrusion is disposed at opposite distal end of each clasp member, so that space between the pair of clasp members, in normal state, shrinks from the joint ends to the distal ones. Each clasp protrusion of the clasp member contacts each clasp hole of the frame member, while the base inserts into each accommodating portion. The compelling bolt is between the pair of the clasp members, and further capable of moving towards the distal ends of the clasp members.