A computer-implemented efficacy evaluation method for evaluating a drug efficacy of a chemical substance upon a cell aggregate, comprising: acquiring a plurality of tomographic images of the cell aggregate which are imaged along cross sections matching with a vertical plane where the cell aggregate is held inside a liquid which is contained in a container and has added the chemical substance; generating a three-dimensional image of a surface of the cell aggregate by image processing based on the plurality of tomographic images; and calculating a feature amount of the cell aggregate as information for determining the drug efficacy of the chemical substance based on the three-dimensional image, the feature amount including a curvature of a surface of the cell aggregate in a cross section viewed from a horizontal direction and a curvature of a surface of the cell aggregate in a cross section viewed from a vertical direction, wherein: tomographic imaging of the cell aggregate is performed a plurality of times at predetermined time intervals; the drug efficacy of the chemical substance is determined based on changes with time of the feature amounts calculated from tomographic images acquired through the imaging; wherein it is determined that the drug efficacy is shown on the basis of a difference between the curvature of a surface of the cell aggregate in a cross section viewed from the horizontal direction and the curvature of a surface of the cell aggregate in a cross section viewed from the vertical direction. acquiring a plurality of tomographic images of the cell aggregate which are imaged along cross sections matching with a vertical plane where the cell aggregate is held inside a liquid which is contained in a container and has added the chemical substance; generating a three-dimensional image of a surface of the cell aggregate by image processing based on the plurality of tomographic images; and calculating a feature amount of the cell aggregate as information for determining the drug efficacy of the chemical substance based on the three-dimensional image, the feature amount including a curvature of a surface of the cell aggregate in a cross section viewed from a horizontal direction and a curvature of a surface of the cell aggregate in a cross section viewed from a vertical direction, wherein: tomographic imaging of the cell aggregate is performed a plurality of times at predetermined time intervals; the drug efficacy of the chemical substance is determined based on changes with time of the feature amounts calculated from tomographic images acquired through the imaging; wherein it is determined that the drug efficacy is shown on the basis of a difference between the curvature of a surface of the cell aggregate in a cross section viewed from the horizontal direction and the curvature of a surface of the cell aggregate in a cross section viewed from the vertical direction. tomographic imaging of the cell aggregate is performed a plurality of times at predetermined time intervals; the drug efficacy of the chemical substance is determined based on changes with time of the feature amounts calculated from tomographic images acquired through the imaging; wherein it is determined that the drug efficacy is shown on the basis of a difference between the curvature of a surface of the cell aggregate in a cross section viewed from the horizontal direction and the curvature of a surface of the cell aggregate in a cross section viewed from the vertical direction.