The invention relates to a forest machine for transport of payload in forest terrain, comprising a frame (9) on which a payload holding device (3, 4) is mountable, which is adapted to hold the payload (2), a drive unit (8) for driving the forest machine, at least six wheels (10) of which at least four are arranged in form of a bogie (11, 12) comprising two bogie arms (13), which each carries two or more rotatable wheels, are positioned on each side of the forest machine with a longitudinal axis in the driving direction of the forest machine and are via a pivot joint (14) pivotal connected to the frame in an area between the at least two wheels. The forest machine is provided with a payload weighing device for detecting the weight of the payload on the forest machine which comprises at least one deflection gauge (15) attached on a surface of at least one of the bogie arms for detecting the magnitude of a deflection of the bogie arm in an angle of 20-70° in relation to a longitudinal axis of the bogie arm. The invention also relates to a method for payload weighing on a forest machine.
