1. A pattern forming method, comprising: forming a physical guide that includes a first pattern in a first region and a second pattern in a second region on an underlying film; applying a polymer material onto the physical guide, to embed the polymer material into a concave portion of the physical guide; microphase-separating the polymer material, to form a self-assembly pattern having a first polymer section and a second polymer section; observing the self-assembly pattern in the second region, to determine from an observation result whether or not the self-assembly pattern in the first region has a predetermined shape; selectively removing the first polymer section in the case of determining that the self-assembly pattern in the first region has the predetermined shape; and processing the underlying film using the physical guide and the second polymer section as a mask, wherein the second pattern includes a pattern with a larger coverage ratio than the first pattern and a pattern with a smaller coverage ratio than the first pattern.