To enable a reference position which is formed on a scale, to be found effectively.

The scale 20 moves depending on a positional fluctuation. An encoder head 10 detects the reference point based on a reference position mark 22 formed on the scale 20. A reference position track which includes a plurality of reference position marks 22, is disposed on the scale 20, and a multi-reference position block being composed of the plurality of reference position marks 22 arranged along a direction in which the scale 20 moves, and non-reference position block having no reference position mark 22, are disposed adjacently on the reference position track along the direction in which the scale 20 moves.

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