The encoder includes a scale and a sensor relatively movable in a first direction. The sensor includes first and second readers reading a first pattern. The encoder acquires a first position in a first direction by using an output signal from the first reader and acquires a second position in the first direction by using an output signal from the second reader. The encoder acquires a period of the first pattern by using the first and second positions, and acquires first and second shift amounts between the scale and the first and second readers in a second direction orthogonal to the first direction. The encoder produces position information by using the first and second positions, the period and the first and second shift amounts.