A thin pivotal apparatus includes a holding seat, an arc-shaped driven member and at least one torsional force generation member. The holding seat includes a base, a housing space and a first assembly portion and a second assembly portion that are located on the base corresponding to two opposite sides of the housing space. The arc-shaped driven member is located in the housing space and includes an operational portion, a curved portion connected to the operational portion and a driving portion extended from the curved portion toward the operational portion to couple with the first assembly portion to form a pivotal relationship. Each torsional force generation member includes a first connection portion located on the second assembly portion, a second connection portion connected to the junction of the driving portion and the curved portion, and a hydraulic portion connected to the first connection portion and the second connection portion.