An outboard motor supporting arrangement includes a stern bracket fixed to a transom of a boat, a lift member which supports the outboard motor and which is connected with the stern bracket so that the lift member is movable up and down and swingable together with the outboard motor, a vertically extending tilt cylinder which is connected between the stern bracket and lift member for causing the lift member to move up and down, and a pair of horizontally extending trim cylinders which are provided between the stern bracket and lift member, for causing the lift member to swing. Each trim cylinder is pivotally supported on the stern bracket, and a rear end of each trim cylinder is provided with thrust rollers which rolls on the lift member. Alternatively, each trim cylinder is pivotally supported on the lift member, and the front end is provided with the thrust rollers abutting against the stern bracket.