A signal processing device includes amplifiers that are capable of amplifying detected signals using amplification factors that are different from each other; A/D converters that sample plural signals amplified by the amplifiers using the different amplification factors and output from the amplifiers; calculators that perform, on the basis of the amplification factors of the plural amplifiers, calculation on plural data pieces converted by the A/D converters; and a selector that selects one or more of output data pieces from among plural data pieces output from the calculators.