PURPOSE: To provide a tape printing device capable of simply printing character strings in an inputted document based upon various character string shapes.

CONSTITUTION: In the case of developing a character string 'ABCD' into dot pattern data by a pattern number '1', the character A is arranged in a printing buffer 35 so that the lower end position of the character pattern matches with an arrangement reference position KP1 to be a base line based upon minimum character size SS. Characters B, C, D are successively arranged in the buffer 35 so that the lower end positions of respective character patterns match with the position KP1 in accordance with successive increment of size in each size variable obtained by calculating the size of each printing character by size variable calculating processing control. Thus the character string 'ABCD' is printed out on a printing tape by a character string format for gradually increasing the character sizes of respective characters in the character string based upon the dot pattern data developed in the buffer 35.