A capacitance sensor detecting an approach of an object to a detection area in which electrodes are arranged, the capacitance sensor comprising: N electrode groups arranged in the detection area which is divided into a plurality of sections (Ai), N being a natural number not less than 2, each electrode group including at least one of the electrodes, wherein each section includes N partial electrodes, each of which being part of an individual electrode belonging to corresponding one of the N electrode groups, wherein each of said N electrode groups is formed by partial electrodes arranged and connected to each other along one and the same direction; a capacitance detection unit configured to detect a capacitance formed between the object and each of the individual electrodes in the N electrode groups, thereby outputting respective detection values for the individual electrodes; a sum calculation unit configured to add detection values of the capacitance obtained by the capacitance detection unit for each of the electrode groups so as to calculate sum totals of the detection values for each of the N electrode groups; and a determination unit configured to determine whether a detection result of the capacitance detection unit is affected by noise based on the N sum totals calculated for the N electrode groups, wherein each of the electrode groups has the same sensitivity ratio in each of the plurality of sections (Ai) and the sensitivity ratio of one of the electrode groups in one of the sections indicates a ratio of an area occupied by the partial electrode belonging to the one of the electrode groups to an area occupied by the N partial electrodes in the one of the sections, and the determination unit is configured to determine whether the detection result of the capacitance detection unit is affected by noise based on ratios among the N sum totals of the N electrode groups and a determination criterion which is set based on ratios among N sensitivity ratios of the N electrode groups. N electrode groups arranged in the detection area which is divided into a plurality of sections (Ai), N being a natural number not less than 2, each electrode group including at least one of the electrodes, wherein each section includes N partial electrodes, each of which being part of an individual electrode belonging to corresponding one of the N electrode groups, wherein each of said N electrode groups is formed by partial electrodes arranged and connected to each other along one and the same direction; a capacitance detection unit configured to detect a capacitance formed between the object and each of the individual electrodes in the N electrode groups, thereby outputting respective detection values for the individual electrodes; a sum calculation unit configured to add detection values of the capacitance obtained by the capacitance detection unit for each of the electrode groups so as to calculate sum totals of the detection values for each of the N electrode groups; and a determination unit configured to determine whether a detection result of the capacitance detection unit is affected by noise based on the N sum totals calculated for the N electrode groups, wherein each of the electrode groups has the same sensitivity ratio in each of the plurality of sections (Ai) and the sensitivity ratio of one of the electrode groups in one of the sections indicates a ratio of an area occupied by the partial electrode belonging to the one of the electrode groups to an area occupied by the N partial electrodes in the one of the sections, and the determination unit is configured to determine whether the detection result of the capacitance detection unit is affected by noise based on ratios among the N sum totals of the N electrode groups and a determination criterion which is set based on ratios among N sensitivity ratios of the N electrode groups.