PURPOSE: To obtain a high-strength sheet having excellent filtration performance, dust-collecting property, etc., by using ultrafine fibers having a specific average fiber diameter and thick fibers composed of a thermoplastic fiber having a melting point lower than the melting point of the ultrafine fiber and partially bonding the ultrafine fiber to the thick fiber with heat.

CONSTITUTION: The objective sheet having excellent bacteria-barrierness, liquid- absorbing property and heat-insulation and suitable as various filters, wipers, laps, heat-insulation materials, etc., is a random mixture of (A) ultrafine fibers having an average fiber diameter of 0.1-0.8μm and composed of polypropylene, polyethylene terephthalate, etc., and (B) thick thermoplastic fibers having an average fiber diameter of ≥10μm and a meting point lower than that of the ultrafine fiber by 10-200°C (e.g., fiber of nylon 6 or polypropylene). The sheet is produced by partially bonding the ultrafine fibers A and the thick fibers B with heat.