The structural, electronic, and superconducting properties of B-doped cubic and hexagonal diamane (single layer diamond) were investigated based on the first-principles methods. B atom tends to stay in the substitutional site, and the most stable configuration is the structure with vertical B-B dimer. The formation energy of B-doped diamane is lower than the counterpart of pristine diamane indicating that B dopant can facilitate the synthesis of diamane. The configurations with vertical B-B dimers are semiconductors with tunable band gaps, which decrease with the B concentration increasing due to the interaction between B-B dimers. For example, the band gap of 3.125 mol% and 6.25 mol% B-doped cubic diamane is 1.82 eV and 1.44 eV, respectively. Moreover, configurations with meta-stable B distributions are metals, which have comparable superconducting transition temperatures with B-doped diamond (~4 K).