We present a method which can evaluate stiffness of cell-spheroids, and show the measurement results of the stiffness changes with respect to the culture time. To obtain the stiffness-index map, where the map shows the relationship between the size and stiffness of cell-spheroids, we applied on-chip measurement method using a robot integrated microfluidic chip (robochip). The robochip has a microchannel and a pair of on-chip probes which contains a force sensor. By measuring the stiffness in microfluidic channel, we can achieve a stable and high-throughput evaluation of mechanical characteristics. The stiffness of the single spheroid is evaluated from the reactive force when the target spheroid is deformed by the on-chip probes. The stiffness-index of cell-spheroid is proposed, and the evaluation results of the stiffness index shows that the index increased along the culture days. The proposed system will provide us a new index for the cell-quality evaluation.