Provided is a block copolymer of a conjugated diene compound and a non-conjugated olefin, a rubber composition including the block copolymer, a crosslinked rubber obtained by crosslinking the rubber composition, and a tire using the rubber composition or the crosslinked rubber composition. The copolymer of the present invention is a block copolymer of a conjugated diene compound and a non-conjugated olefin, the copolymer having a peak area in a temperature range in a range of 70° C. to 110° C. that accounts for at least 60% of a peak area in a range of 40° C. to 140° C. and a peak area in a range of 110° C. to 140° C. that accounts for 20% or less of a peak area in a range of 40° C. to 140° C., the peak areas being measured by the differential scanning calorimetry (DSC) according to JIS K 7121-1987.