To eliminate mirror work of an internal wall surface in a tank case, easily and inexpensively separate operating oil and gas in a tank device, so that suction of gas by a pump device can be prevented.

In a tilt trim device 17 for an outboard engine having a hydraulic cylinder device 18 arranging a piston rod 25 and a piston 24 in a cylinder 21 to be charged with operating oil, pump device supplying operating oil to the hydraulic cylinder device, and a tank device 20 accumulating operating oil from the hydraulic cylinder device to generate power by extending/ contracting action of the hydraulic cylinder device, the tank device, arranging in a tank case 23 an independent bubble aggregate 55 having a space 58 with an internal wall surface of the tank case, is constituted capable of separating operating oil and gas.