To provide an oil passage switching device in a rocker arm in which switching is performed without problems by a simple mechanism even when a working fluid used for valve opening/closing for example is supplied through the same oil passage in a rocker shaft as that of a lubricating oil supplied to other members, and to provide a valve mechanism using the oil passage switching device.

This rocker shaft of the rocker arm is provided with a rocker shaft rotating means for axially rotating the rocker shaft. The rocker shaft rotating means rotates the rocker shaft so as to perform connection or cut-off between a hydraulic port for working fluid and a control port. A hydraulic port for lubricating oil and a supply port are formed so as to always connect to each other regardless of a position of the rocker shaft rotated by the rocker shaft rotating means.