The evolution of giant molecular clouds (GMCs) is an essential process for unraveling the galaxy evolution. We analyzed 12CO(J=2-1) data of the nearest spiral galaxy M33 obtained with the ALMA 7m array combined with the IRAM 30m data to investigate the GMC evolution. It covers most of the molecular-gas disk at 39 pc resolution. We identified more than 700 GMCs and classified them into three GMC types based on the Ha luminosity L(Ha); Type I: associated with no HII regions, Type II: associated with HII regions of L(Ha) < 10^37.5 erg/s, Type III: associated with HII regions of L(Ha) > 10^37.5 erg/s. We found that mass, size, velocity dispersion, and density increase monotonically from Type I to III. Type I and II GMCs are distributed in both the spiral arm and the inter-arm, while most of Type III GMCs exist in the spiral arm and show the highest spatial correlation with young stellar clusters. These facts suggest that GMCs evolve in the order of Type I, II, and III, and that the gravitational potential of the spiral arms can induce active star formation.
Furthermore, we performed ALMA 12CO, 13CO, C18O(J=2-1) observations toward three most massive (~10^6Msun) GMCs in M33 at 1pc resolution. The target GMCs are at different evolutionary stages: GMC-8 with inactive star formation; NGC604, one of the most luminous HII regions; and GMC-16, associated with relatively small HII regions. NGC604 and GMC-16 contain many filamentary structures, while GMC-8 has less filamentary structures and significantly lower 13CO/12CO ratios. These results indicate that the dense gas fraction in GMCs increases as the star formation progresses. We also suggest that the impact of spiral arms and/or tidal interaction caused cloud-to-cloud collisions that triggered the formation and growth of the GMCs and the formation of high-mass stars in the GMCs.