PURPOSE: To produce a high strength multifiament having a high flexural stiffness and particular usefulness for manufacturing a textile sheet material for use in a hot and moist environments by a simple production method.

CONSTITUTION: The bonded yarn bundle comprises at least one twisted multifilament yarn composed of a first synthetic polymer in a state in which individual filaments are bonded to each other over essentially the entire cross section of the textured yarn by the melting of a second thermoplastic synthetic polymer having the melting point at least 10°C below the melting point or decomposition point of the first synthetic polymer, e.g. polyethylene terephthalate. The bonded yarn bundle has at least 38 cN/tex tenacity. The bonded yarn is notatable for a high strength, good flexural stiffness and good hydrolysis resistance, and is usable as a textile sheet material usable in hot and moist environments, especially wire cloth for a papermaking machine.