Provided are: a fiber-containing material which has improved strength in an out-of-plane direction without a decrease in strength in an in-plane direction; a method for inserting out-of-plane reinforcement threads; and a method for producing the fiber-containing material. The fiber-containing material contains a base material and out-of-plane reinforcement threads. The base material contains reinforcement fibers extending in a direction along a plane. The out-of-plane reinforcement threads are formed in the base material so as to extend in a direction intersecting the direction along the plane.