A pattern forming apparatus comprising: a rotary drum that includes a cylindrical outer circumferential surface which is curved at a predetermined radius from a predetermined center line, that rotates about the center line in a state in which a part of a sheet substrate is supported in a length direction of the sheet substrate along the outer circumferential surface; a pattern forming part that forms the pattern on the sheet substrate at a first specific position; a scale disk that is fixed to an end portion of the rotary drum in a direction in which the center line extends while being coaxial with the center line and that includes a circular scale; and a first reading mechanism that is arranged to oppose with the scale formed at the outer circumferential surface of the scale disk, that is arranged at substantially same azimuth as an azimuth.