Direct Observation of the Surface Superconducting Gap in the Topological Superconductor Candidate <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mi>β</mml:mi> <mml:mtext>−</mml:mtext> <mml:msub> <mml:mrow>

β-PdBi_{2} is one of the candidates for topological superconductors with a superconducting (SC) transition temperature (T_{c}) of 5.3 K, in which parity mixing of a spin singlet and spin triplet has been anticipated, being crucial for the further understanding of the relationship with inversion symmetry and parity mixing in the superconductivity. In this Letter, we measured the SC gap in a high-quality single crystal of β-PdBi_{2} by using high-resolution laser angle-resolved photoemission spectroscopy below T_{c}. We found the isotropic SC gaps in momentum space for multiple bands, and observed that the difference between the SC gap of the topological surface bands and the bulk bands is about 0.1 meV, consistent with other experimental results. These direct and quantitative experimental results support the possibility of β-PdBi_{2} as a topological superconductor, characterized by unique crystal and electronic band structures.