A stroker tool for providing an axial force in an axial direction of a downhole tool. The stroker tool has a pump, a driving unit for driving the pump, and an axial force generator. The generator has an elongated piston housing having a first and a second end, and a piston provided on a shaft, and the shaft penetrates the housing for transmitting the axial force to another tool. The piston is provided in the piston housing so that the shaft penetrates the piston and each end of the piston housing and divides the housing into a first and a second chamber, and the first and the second chamber are each fluidly connected to the pump via at least one duct so that the pump can pump fluid into one chamber by sucking fluid from the other chamber for moving the piston within the housing, and thereby moving the shaft back and forth.