To provide a sealing material improving dynamic durability, ensuring mechanical characteristics favorable as the sealing material such as low stress and high elongation and further having good operation efficiency.

The dynamic durability of the sealing material characterized as comprising an oxyalkylene polymer (A) having 20,000-50,000 number-average molecular weight and ≥0.8 reactive silicon group on the average in one molecule, a plasticizer (B) in an amount of >10 pts.wt. based on 100 pts.wt. of the polymer (A), a filler (C) and a curing catalyst (D) is improved. Thereby, the problems are solved.