It increases it by 1.5 or 50% of the Base power.
Meaning moves like Bug bite, would go from 60 power, to 90.
Technician increases the base power of all moves which have a base power of 60 or less by 1.5×.
For moves with variable base power, Technician will only apply if the base power is 60 or less when used. Thus, Pursuit will not get a Technician boost if the opposing Pokémon switches and Pursuit's base power doubles to 80. Similarly, if a move like Avalanche is used by a Pokémon previously damaged in the same turn, which doubles Avalanche's base power to 120, then Technician will not be applied.
The effect does not apply to confusion damage, which remains at a base power of 40.