A multi-purpose ladder with improved rungs has two ladder sections, and each of the ladder sections comprises two inner rails attached with inner rungs and two outer rails attached with outer rungs. Each of the inner rungs is composed of an upper rung member, a square pipe shaped intermediate rung member, and a lower rung member. The upper rung member and the lower rung member each have a slant pedal section and two support sections. The two support sections join the upper and lower side of the intermediate rung member and the slant pedal section. The slant pedal section inclines an angle corresponding to the outer rungs such that the inner rungs provide strong strength for being stepped on.