Disclosed is a near-infrared absorbing compound which does not contain antimony or arsenic, and has excellent stability, especially excellent heat resistance, light resistance and moist heat resistance. Also disclosed are a near-infrared absorbing filter, which is produced by using the near-infrared absorbing compound, and has excellent resistance such as light resistance and heat resistance, an optical filter and an optical recording medium. Specifically disclosed are a diimmonium compound represented by the formula (1) below and a near-infrared absorbing filter obtained by using such a diimmonium compound. Further specifically disclosed are a near-infrared absorbing filter wherein an adhesive layer containing the diimmonium compound is arranged on a transparent supporting body, and an optical filter using such a near-infrared absorbing filter. ##STR00001## (In the formula (1), R.sub.1 to R.sub.8 independently represent a hydrogen atom or an optionally substituted aliphatic hydrocarbon residue; R.sub.9 to R.sub.11 independently represent an aliphatic hydrocarbon residue which may have a halogen atom; and rings A and B may further have a substituent).