The present invention provides a nanowire sensor comprising nanowires, in which the nanowires are stacked to form a three-dimensional structure so that they have a large exposed surface area compared to that of a conventional straight nanowire sensor in the same limited area, thereby increasing the probability of attachment of a target material to the nanowires to thereby increase the measurement sensitivity of the sensor. Thus, a change in the electrical conductivity (conductance or resistance) of the nanowires can be sensed with higher sensitivity, suggesting that the sensor has increased sensitivity.