A rotation detection device includes a detection unit and a determination circuit unit. A first magnetoresistive element pair, a second magnetoresistive element pair and a third magnetoresistive element pair are located to be farther from the end part than a fourth magnetoresistive element pair and a fifth magnetoresistive element pair are. The second magnetoresistive element pair is located in a region surrounded by the first magnetoresistive element pair, the third magnetoresistive element pair, the fourth magnetoresistive element pair and the fifth magnetoresistive element pair. The detection unit is to generate a main signal based on outputs of the first magnetoresistive element pair, the second magnetoresistive element pair and the third magnetoresistive element pair and to generate a sub signal based on outputs of the fourth magnetoresistive element pair and the fifth magnetoresistive element pair.