Many plant species need pollinators for their reproduction. However, pollinators are declining because of the environmental changes such as agricultural intensification. Bumblebees are one of the pollinators, and also declining. Urban gardens have been increasing its importance as foraging and nesting sites for pollinators. Bumblebees are also said that they get advantages of garden flowers. Bumblebees have some extent of floral constancy. These foraging patterns would be different between sites and seasons with different flower species diversities. So, we compared foraging patterns of bumblebees ( Bombus spp.) between urban and natural forests. For the comparisons, we used bumblebee foraging plant species numbers as an index of foraging patterns, and counted the numbers of pollen species on bee’s bodies. We defined plant species that accounted for more than 10% of total pollens on bee’s body as major foraging species, and compared major foraging species numbers and total foraging species numbers of individual bees between sites and seasons. Also we compared major foraging species numbers and total foraging species numbers of individual species (major niche width and total niche width). The foraging patterns of bumblebees changed between sites and seasons affected by flowering species numbers, floral structure, and bumblebee lifecycles. Urban site provided foraging and nesting sites to bumblebee species that don’t survive in forests. It also revealed that the large number of flower species in urban site enabled some bumblebee species to reduce intra-specific competitions.