1. An image analyzer for detecting a target object from image data, the image analyzer comprising: a reference detection unit that detects a reference object included in the image data; a primary detection unit that detects candidates for the target object from the image data; a secondary detection unit that specifies a portion including the target object from among the candidates, by using a correlation between a feature of the detected reference object and a feature of the candidates; and an output unit that outputs information representing the portion including the target object specified by the secondary detection unit.