A fluid-pressure-operated valve timing controller includes an outer rotor, an inner rotor, and a spiral spring constructed by an element wire spirally extending. The spiral spring biases the inner rotor in a biasing direction when the spiral spring twistingly deforms in accordance with sliding rotation of the inner rotor in a deformation direction relative to the outer rotor. The spiral spring has a bent part bent to protrude in a radial direction. The bent part of the spiral spring is linearly contact with a part of the element wire located adjacent to the bent part in the radial direction.