To obtain the subject fluid having high electroviscous effect under applied voltage, capable of being stably used and useful for shock absorbers, clutches, etc., of mobile equipment by including specific spherical carbonaceous powder and specific insulating oil.

This electroviscous fluid comprises (A) spherical carbonaceous powder obtained by using a condensate of an aromatic sulfonic acid (salt) by methylene type bond (e.g. carbonaceous powder, in which deviations of maximum diameter and minimum diameter to average diameter are each ≤30% of average diameter, having 0.1-20 μm average particle diameter), (B) an insulating oil having ≥3 relative permittivity (e.g. fluorosilicon oil or a mixture of the fluorosilicon oil with silicone oil having 1-100 μm2/s kinematic viscosity at 25°C) and as necessary further (C) 0.01-5 wt.% modified silicone oil.