To reduce expansion and contraction due to change in the temperature of a member to be read (a linear scale) of a linear motor as much as possible.

A position detection means 14 comprises a member 14b (linear scale) to be read that is mounted to one member (frame 7) of the relative movement apparatus via a base 15, and a read head 14a for reading the member 14b to be read that is mounted to the other (carriage 11) of the relative movement apparatus. In the position detection means 14, the member 14b to be read is stuck to the base 15 and at the same time follows expansion and contraction in the relative movement direction of the base 15 due to change in temperature. At the same time, the base 15 is fixed to the relative movement direction at one base point and at the same time the base is slidably mounted to one member at least at one movable point in the relative movement direction.