A detection device including n number of sensors arrayed in a direction, in which n is an integer of 3 or more and from which (n−1) pairs of adjacent sensors are formed, and a processor which determines one specified position in the direction based on output values of the n number of sensors, in which the processor calculates (n−1) sets of difference values each of which is a difference between two output values corresponding to each of the (n−1) pairs of sensors, and determines the one specified position based on the (n−1) sets of difference values and correlation positions corresponding to the (n−1) sets of difference values and indicating positions correlated with array positions of each pair of sensors.