Aromatic polysulfone, prepreg, and method for producing prepreg

An aromatic polysulfone which is a thermoplastic aromatic polysulfone obtained by polymerizing a dihalogeno compound (A) represented by a formula (A) and a dihydric phenol (B) represented by a formula (B),

• wherein a value of a ratio (Mw/Mn) between a number average molecular weight (Mn) and a weight average molecular weight (Mw) is at least 1.80 and less than 1.90,
• the number average molecular weight (Mn) is at least 6,000 and less than 9,200, and
• the glass transition temperature of the aromatic polysulfone is 215° C. or higher and 235° C. or lower;
• wherein in the formulas (A) and (B), each of X and X′ independently represents a halogen atom;
• each of R1, R2, R3 and R4 independently represents an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms;
• each of n1, n2, n3 and n4 independently represents an integer of 0 to 4;
• and
• when n1, n2, n3 or n4 is an integer of 2 to 4, a plurality of R1, R2, R3 or R4 groups may be the same or different from each other.