A microstructure production method comprising: a photoresist pattern forming step of irradiating a positive photoresist applied onto a base material (10, 50) with laser light while scanning the laser light to expose the photoresist to light, and developing the photoresist, thereby forming a photoresist pattern having a surface patterned with a concave and convex, wherein in the photoresist pattern forming step, an overlay exposure process in which exposure of a plurality of gradations with a modulated amount of laser light depending on an in-plane position of the base material (10, 50) is carried out one upon another and multiple times is performed by setting gradation patterns with different relations between the in-plane position of the base material (10, 50) and the amount of laser light so that the number of gradations of a total amount of exposure in the overlay exposure process is increased compared to the number of gradations of the modulation of the amount of the laser light, and the concave and convex pattern according to the total amount of exposure in the overlay exposure process is formed after developing the photoresist, and in the overlay exposure process, the exposure of the photoresist is carried out one upon another by using exposure pattern data different from that used in a previous exposure as exposure pattern data representing a relation between a relative position and the amount of laser light, or is carried out one upon another by using the same exposure pattern data as that used in a previous exposure as exposure pattern data representing a relation between a relative position and the amount of laser light and by shifting the in-plane position of the base material (10, 50) of the exposure pattern data. a photoresist pattern forming step of irradiating a positive photoresist applied onto a base material (10, 50) with laser light while scanning the laser light to expose the photoresist to light, and developing the photoresist, thereby forming a photoresist pattern having a surface patterned with a concave and convex, wherein in the photoresist pattern forming step, an overlay exposure process in which exposure of a plurality of gradations with a modulated amount of laser light depending on an in-plane position of the base material (10, 50) is carried out one upon another and multiple times is performed by setting gradation patterns with different relations between the in-plane position of the base material (10, 50) and the amount of laser light so that the number of gradations of a total amount of exposure in the overlay exposure process is increased compared to the number of gradations of the modulation of the amount of the laser light, and the concave and convex pattern according to the total amount of exposure in the overlay exposure process is formed after developing the photoresist, and in the overlay exposure process, the exposure of the photoresist is carried out one upon another by using exposure pattern data different from that used in a previous exposure as exposure pattern data representing a relation between a relative position and the amount of laser light, or is carried out one upon another by using the same exposure pattern data as that used in a previous exposure as exposure pattern data representing a relation between a relative position and the amount of laser light and by shifting the in-plane position of the base material (10, 50) of the exposure pattern data.