Provided is a fluid monitoring method including photographing a particle in a flowing fluid using a first camera, photographing the particle using a second camera spaced apart from the first camera, and analyzing the particle using images captured by each of the first camera and the second camera, in which the analyzing of the particle includes calculating a volume of the particle, calculating a velocity of the particle moving in the fluid, calculating a density of the particle using the volume and the velocity, and identifying a type of the particle using the density.