PURPOSE: To make possible easy and rapid adjustment with high connection accuracy by setting the spacing between detection heads at the integer times of magnetic grating pitch and interposing connection part between magnetic scales.

CONSTITUTION: Spacing between detection heads 1, 2 such as two magnetic flux response type multigap heads, etc. is so fine-adjusted as to become the integer times of the magnetic grating pitch of magnetic scales and is accurately set, after which the connection part 9 between the magnetic scales 3, 3' to be connected is interposed between these detection heads 1, 2. Here, the detection heads 1, 2 are mechanically fixed in this position and is fixed in the position where the phase differences between the magnetic scales 3, 3' become zero by fineadusting the position of the magnetic scale 3', thence the magnetic scales 3, 3' are connected. Thereby, even the magnetic scales of high accuracy and long length may be readily connected