A method of electrochemically producing a hydrogel (101, 102, 103, 105, 106, 107) by using electrolytic deposition of the hydrogel (101, 102, 103, 105, 106, 107), the method by which the hydrogel (101, 102, 103, 105, 106, 107) is formed by a reaction which is induced in an electrolytic solution by an electrode product electrochemically generated by electrodes (20, 20 1, 20 2, 20 3, 30, 120, 121, 122) installed in the electrolytic solution, the method comprising: a preparing step of providing an apparatus including an electrolytic tank and housing an electrolytic solution therein, the electrolytic tank having a two-dimensional array of working electrodes (20, 20 1, 20 2, 20 3) provided on a bottom surface thereof and a counter electrode installed therein, the electrolytic solution containing a dissolved substance which causes electrolytic deposition of the hydrogel (101, 102, 103, 105, 106, 107); a first step of forming the hydrogel (101, 105, 106) with a two-dimensionally defined first pattern on the bottom surface, by applying a first voltage as a predetermined voltage to a first working electrode group as one or more selected working electrodes of the two-dimensional array of the working electrodes (20, 20 1, 20 2, 20 3), the first pattern corresponding to an arrangement of the selected working electrodes (20, 20 1, 202, 203); and a second step of forming the hydrogel (102, 105, 106) with a two-dimensionally defined second pattern on the bottom surface, by applying a second voltage as a predetermined voltage to a second working electrode group as one or more selected working electrodes of the two-dimensional array of the working electrodes (20, 20 1, 20 2, 20 3), the second pattern corresponding to an arrangement of the selected working electrodes (20, 20 1, 20 2, 20 3), wherein the second step is performed after the first step, and the hydrogel (103, 107) with a three-dimensionally defined pattern including at least two layers is formed such that one of the two layers having the second pattern is located under the other of the two layers having the first pattern on a side thereof closer to the bottom surface. a preparing step of providing an apparatus including an electrolytic tank and housing an electrolytic solution therein, the electrolytic tank having a two-dimensional array of working electrodes (20, 20 1, 20 2, 20 3) provided on a bottom surface thereof and a counter electrode installed therein, the electrolytic solution containing a dissolved substance which causes electrolytic deposition of the hydrogel (101, 102, 103, 105, 106, 107); a first step of forming the hydrogel (101, 105, 106) with a two-dimensionally defined first pattern on the bottom surface, by applying a first voltage as a predetermined voltage to a first working electrode group as one or more selected working electrodes of the two-dimensional array of the working electrodes (20, 20 1, 20 2, 20 3), the first pattern corresponding to an arrangement of the selected working electrodes (20, 20 1, 202, 203); and a second step of forming the hydrogel (102, 105, 106) with a two-dimensionally defined second pattern on the bottom surface, by applying a second voltage as a predetermined voltage to a second working electrode group as one or more selected working electrodes of the two-dimensional array of the working electrodes (20, 20 1, 20 2, 20 3), the second pattern corresponding to an arrangement of the selected working electrodes (20, 20 1, 20 2, 20 3), wherein the second step is performed after the first step, and the hydrogel (103, 107) with a three-dimensionally defined pattern including at least two layers is formed such that one of the two layers having the second pattern is located under the other of the two layers having the first pattern on a side thereof closer to the bottom surface.