PURPOSE: To provide a titled device which automates doming and performs doming to a uniform shape by constituting said device wherein while air is supplied, via a rotating body, into a vertically gripped glass tube under rotation from the opening at the top end thereof and the part near the bottom end of the glass tube is closed by melting from the outside.

CONSTITUTION: A glass tube 3 having openings at both ends is gripped and rotated by means of three rolls (not shown in the figure) moved forward and backward by the cam and spring (not shown) operated by an air cylinder 34, a piston rod 35, etc. centripetally and centrifugally with respect to the outer circumferential surface of the glass tube 3 in a gripping and rotating part 6 which supports the tube 3 with a support 8 attached to a stanchion 1; in addition, a thrust force is applied on the upper part of the tube. On the other hand, a rotating body 43 having a flange 47 attached to the base 39 in a supporting part 38 is inserted and mounted in the opening 4 at the top end, and while air is supplied, via a connection part 48 to an air source, to the inside of the tube 3, the part near the bottom end 5 of the tube 3 is melted by heating from the outside with a gas burner 50. The bottom end 5 is thus cut and dropped, and the bottom end of the tube 3 is domed easily to a uniform shape by the air pressure exerted in the inside thereof.