A transformer includes: an upper primary substrate (110) which is formed by stacking a plurality of dielectric substrates, each substrate being provided with spiral conductive patterns; a lower secondary substrate (120) which is formed by stacking a plurality of dielectric substrates, each substrate being provided with spiral conductive patterns, in which the lower secondary substrate is positioned below the upper primary substrate (110) in such a way that the lower secondary substrate comes into contact with the upper primary substrate (110) or is spaced apart from the upper primary substrate (110); and a secondary coil element (200) of a planar shape to produce an induced current by a current applied to the upper primary substrate (110) and the lower primary substrate (120).