A Thomson parabola spectrometer for on-line ion detection was constructed to apply to laser driven ion acceleration experiments using cluster targets. We have demonstrated the energy analysis of ions accelerated by the Coulomb explosion of the CO2 clusters using the present apparatus at the J-KAREN laser facility of the National Institutes for Quantum and Radiological Science and Technology. The maximum energy of the detected ions was 2.5 MeV/q, which was corresponding to about 0.9 MeV/u in converting to energy per nucleon. This result is consistent with the results obtained using CR-39. It was shown that the present apparatus is very useful for searching optimal experimental parameters and measuring ion energy owing to the characteristic of on-line ion detection.