To provide a pattern forming device, pattern forming method, etc., capable of preventing displacement with a previous process pattern.

The pattern forming device 100 measures the elongation and contraction of a base material length (step 902) and measures the position of the previous process pattern (step 904) relating to the region where the elongation and contraction ratio ((L+ΔL)/L) of the base material length is not within a prescribed range (No of step 903). The pattern forming device calculates drawing data based on the measurement data (measurement data of the elongation and contraction of the base material length, the measurement data of the position of the previous process pattern) and performs the formation of the fresh pattern based on the drawing data (step 905). The pattern forming device performs the pattern formation by simultaneously irradiating the pattern with a plurality of beams of varying intensity through a plurality of channel light valves, a plurality of irradiation heads, etc.