sites of the composite structural element 10 and making the composite structural element 10 have a wider application range in addition because the interlayers 22 are uniformly distributed in the laminate and have a very small thickness the uniform distribution of force can be ensured and the delamination can be avoided so as to maintain the structural stability of the composite structural element 10 further referring to fig4 in order to manufacture the composite structural element 10 the following steps may be carried out a taking a laminate formed by laminating each of the composite layers 21 with each of the interlayers 22 and winding to form a tubular outer portion 20 b taking an elongated core 41 to coaxially pass through the inner space of the outer portion 20 c exerting an external forces such as an air pressure to the external side of the outer portion 20 such that the outer portion is contracted and attached to the periphery of the core 41 and d wrapping the outer portion 20 onto the core 41 and curing when the step d is carried out if the outer portion 20 is integrally formed with the core 41 so that the core 41 cannot be separated from the outer portion after molding the core 41 becomes the inner portion 30 of the composite structural element 10 as shown in a of fig4 for this reason a lightweight material such as foams or other foamed plastics is preferably used as the material of the core so as to achieve the purpose and effect of lightweight in contrast if after the step d is carried out it is necessary to separate the core 41 from the cured outer portion 20 when the step d is carried out a possibility of separating the outer.