An electrochemical measurement device comprising: a solution well being adapted for containing a solution and a biological sample, the biological sample being any of a cell, a cell aggregate, a piece of tissue, and a non-biological tangible object containing a biologically-relevant substance, wherein the solution well has a flat surface, the flat surface being a bottom surface of the solution well; a plurality of working electrodes provided in the solution well, the plurality of working electrodes including electrode surfaces capable of supplying or receiving electrons to or from a chemical substance to cause an oxidation-reduction reaction, the chemical substance being generated or consumed in the biological sample immersed in the solution, wherein all of the electrode surfaces have a diameter dimension d el not more than 80 μm and are arrayed on the flat surface in a configuration in which a plurality of electrode rows, each of which has a plurality of the electrode surfaces arranged in a straight line in a first direction, is arranged in a second direction orthogonal to the first direction, a spacer (11, 51) fixed on the flat surface, the spacer (11, 51) having a profile surface at a distance h 1 in a direction perpendicular to the flat surface, the distance h 1 satisfying h 1 = 21.8 d el + 0.8 / d el + 9.7 ± 5 μm, the spacer (11, 51) for preventing the biological sample, provided that the biological sample has a diameter not less than 100 μm and not more than 600 μm, from entering a region on a side with the flat surface of the profile surface and to enable a dissolved substance in the solution to diffuse therethrough, wherein the spacer (11, 51) is composed of either a group of pillar structures which extend in the direction perpendicular to the flat surface and stand at intervals less than 100 μm or a porous structure having a pore diameter less than 100 μm, and at least one wall plate fixed between two of the electrode rows adjacent to each other on the flat surface, the at least one wall plate extending in the first direction alongside two or more electrode surfaces arranged in one of the two of the electrode rows such that each of the electrode rows is separated from each of the neighboring rows by one of the at least one wall plate, the at least one wall plate having a height not less than height h 1 of the spacer (11, 51) from the flat surface, and being impervious to the dissolved substance in the solution. a solution well being adapted for containing a solution and a biological sample, the biological sample being any of a cell, a cell aggregate, a piece of tissue, and a non-biological tangible object containing a biologically-relevant substance, wherein the solution well has a flat surface, the flat surface being a bottom surface of the solution well; a plurality of working electrodes provided in the solution well, the plurality of working electrodes including electrode surfaces capable of supplying or receiving electrons to or from a chemical substance to cause an oxidation-reduction reaction, the chemical substance being generated or consumed in the biological sample immersed in the solution, wherein all of the electrode surfaces have a diameter dimension d el not more than 80 μm and are arrayed on the flat surface in a configuration in which a plurality of electrode rows, each of which has a plurality of the electrode surfaces arranged in a straight line in a first direction, is arranged in a second direction orthogonal to the first direction, a spacer (11, 51) fixed on the flat surface, the spacer (11, 51) having a profile surface at a distance h 1 in a direction perpendicular to the flat surface, the distance h 1 satisfying h 1 = 21.8 d el + 0.8 / d el + 9.7 ± 5 μm, the spacer (11, 51) for preventing the biological sample, provided that the biological sample has a diameter not less than 100 μm and not more than 600 μm, from entering a region on a side with the flat surface of the profile surface and to enable a dissolved substance in the solution to diffuse therethrough, wherein the spacer (11, 51) is composed of either a group of pillar structures which extend in the direction perpendicular to the flat surface and stand at intervals less than 100 μm or a porous structure having a pore diameter less than 100 μm, and at least one wall plate fixed between two of the electrode rows adjacent to each other on the flat surface, the at least one wall plate extending in the first direction alongside two or more electrode surfaces arranged in one of the two of the electrode rows such that each of the electrode rows is separated from each of the neighboring rows by one of the at least one wall plate, the at least one wall plate having a height not less than height h 1 of the spacer (11, 51) from the flat surface, and being impervious to the dissolved substance in the solution.