A congestion sign detection method that is executed by a congestion sign detection device 10 which includes three-dimensional acceleration sensor 14 that acquires acceleration information in each axis direction of an X axis, a Y axis, and a Z axis forming an orthogonal coordinate system of the three-dimensional space. The method includes: an input data calculation step of calculating an acceleration vector using the acceleration information acquired by the three-dimensional acceleration sensor 14, and calculating a norm of a difference of the vectors at two different timings as input data; a frequency analysis step of calculating an autocorrelation of the input data and calculating a power spectrum by performing a Fourier transform on the autocorrelation; an angle information acquisition step of converting the power spectrum into angle information; and a congestion sign detection step of detecting congestion sign according to the angle information.