Abstract: An adjustable position fixing apparatus for fixing instruments such as an endoscope and an illuminator in a desired spatial position is provided. The adjustable position fixing apparatus for an instrument and the like comprises a cylinder communicating with a pressure fluid supplying machine, such as a compressor, through a switching device, a mount member for mounting an instrument and the like thereon, and an adjustable bending arm portion through which a linear element such as a wire extends. The arm portion is disposed between the cylinder and the mount member over an entire area or a part thereof. One end of the linear element is attached to a reciprocating rod of the cylinder and the other end is attached to the mount member.