Abstract: In dispersing a fine carbon fiber in a thermosetting resin, the invention disperses and disentangles the fine carbon fiber being aggregates form in the thermosetting resin solution, maintains the stable dispersed state, lowers the viscosity of the thermosetting resin solution in which the fine carbon fiber is dispersed, and provides a thermosetting resin formed article containing the fine carbon fiber by curing the fine carbon fiber dispersion solution and a production method thereof. The thermosetting resin-containing solution in which a fine carbon fiber is dispersed, comprises a thermosetting resin, the fine carbon fiber and a viscosity-decreasing agent for fine carbon fiber having a chemical structure represented by the following general formula (1), wherein R1 to R7 are hydrogen atoms or the like, R5 and R6 may be bonded together to form a ring, and all of them have not more than 30 carbon atoms.