In this study, the superconducting gap symmetry of LaO0.5F0.5BiSSe is elucidated through specific heat measurements with one single crystal of LaO0.5F0.5BiSSe. A clear jump is observed at 3.95 K in LaO0.5F0.5BiSSe, suggesting bulk superconductivity. From specific heat measurements, Delta C-e/gamma T-c and 2 Delta(0)/k(B)T(c) are obtained as 2.31 and 4.5. These values indicate strong electron-phonon coupling superconductivity. The temperature (T) and magnetic-field (H) dependence of the electronic specific heat C-e(T, H) suggests that superconductivity is fully gapped. Our handmade system successfully elucidates superconducting gap symmetry of the BiS2-based compound with a small single crystal.