The present invention discloses an organic-inorganic composite filler that contains: inorganic aggregate particles formed by aggregation of inorganic primary particles with an average particle diameter of 10 to 1000 nm; an organic resin phase including a cured polymer of a polymerizable monomer covering surfaces of the inorganic primary particles and bonding the inorganic primary particles to each other, and a water absorbing resin; and aggregation gaps with a volume of micropores formed between parts of the organic resin phase of 0.01 to 0.30 cm 3 /g in pore volume measurement within a pore diameter range of 1 to 500 nm, as measured by a mercury intrusion technique. In a cross section passing through the centers of the inorganic aggregate particles, based on 100 measured inorganic particles, there are 10 or less inorganic aggregate particles having a macro void with a maximum width of at least 1 µm. The present invention also discloses a method for producing the organic-inorganic composite filler.