A multi-degree-of-freedom displacement measuring device includes a rotary scale that has a scale pattern including a plurality of patterns that are arranged around a first rotation axis and arrayed along a circumference direction of the rotary scale, a detection head group including a plurality of detection heads, each of which is provided around the first rotation axis, is arranged on an installation face facing the rotary scale, and is configured to detect each of the plurality of patterns from the scale pattern, and a calculator configured to, based on detection values acquired by the plurality of detection heads, calculate a relative rotation angle around the first rotation axis, and calculate at least one of a relative movement amount in a direction along the first rotation axis and a relative movement amount in a direction along a second rotation axis orthogonal to the first rotation axis.