The present invention aims to provide method and apparatus to measure paper fiber orientation adapted to measure fiber orientation in this paper from an image to be measured formed by light beam transmitted through paper on the paper side opposite to the incident side thereof improved so that the fiber orientation in this paper being running through a paper making machine can be reliably on-line measured. Paper web (W) is irradiated practically at a right angle thereto with light beam emitted from a pulse laser source (1) and unpolarized through a condenser lens (2) and an image to be measured formed on a surface of the paper web (W) opposite to its incident surface is picked up by a CCD camera (3). An image pick-up optical system (3b) of the CCD camera (3) uses an extra depth-of-field lens. The image picked up in this manner is then image processed for elliptic approximation. Then a fiber orientation angle relative to a major axis of the obtained ellipse and a magnitude of fiber orientation based on a difference or a ratio between the major and minor axes of this ellipse are calculated. Pick-up by the CCD camera (3) may be carried out at predetermined periods and with an appropriate pulse width to pick up a target image as if the paper web (W) is in stationary state.
