Various embodiments improve accuracy by increasing the number of atoms engaged in a clock transitions in an optical lattice clock. An exemplary optical lattice clock an embodiment comprises an optical waveguide, an optical path, a laser light source, and a laser cooler. The optical path has a hollow pathway that extends from a first end to a second end while being surrounded with a tubular wall, which is used as a waveguide path. The optical path passes between mirrors and through the pathway. The laser light source supplies to the optical path a pair of lattice lasers (L1 and L2) propagating in opposite directions with each other. The laser cooler supplies cooled atoms that have two levels of electronic states associated with a clock transition to the vicinity of the first end of the optical waveguide.