PURPOSE: To attain the smallness in size by generating a pressure of oil by a propeller shaft power transmitting means and linearly moving by this pressure of oil a linear motion means fitted to a propeller shaft further converting the linear motion into the rotating motion so as to drive a pitch changing means, in case of the captioned propeller pitch variable device.

CONSTITUTION: A pitch is changed by operating a lever turning a clutch shaft 6 and a cam plate 9, and a pin 25 is moved in a left direction moving a spool shaft 24. Here a pump 21 generates a pressure of oil passing through in a spool 24 and in a piston 28 and acting on a hydraulic cylinder 27, and a shifter 31 performs a linear motion along a spline 30b. Then this linear motion is converted into a rotary motion by a helical spline 32 rotating a transmission sleeve 33. Thus rotating a thread shaft 57 fitted to a propeller boss 34, a propeller 36 changes its pitch through a cross head 39 and a crank 38. In this way, the smallness in size can be attained.